Bump mono

Commit list for mono/mono:

* mono/mono@c8906bed28 [corlib] Disable ThreadPoolTest.GetAvailableThreads () on machines with many cores
* mono/mono@e21641dab1 [crash] Detect when 0 attached threads, fix hang/double-fault.
* mono/mono@8ebb772f86 [2019-02] Bump bockbuild to get GTK fix
* mono/mono@db0df0733d Ensure that the module cctor is run before the entry point is executed (#13242) (#13299)
* mono/mono@1e36288b8e [jit] Avoid an assert when gsharedvt enums are boxed. (#13306)
* mono/mono@4a0e34d358 [2019-02] [linker] Fix monotouch tests which need Xamarin.iOS.dll (#13294)
* mono/mono@c7e155b4a7 [2019-02] Fix mono conc hashtable lookup endless loop (#13291)
* mono/mono@58faa215f4 [2019-02] [interp] mixed mode fixes for delegates (#13259)
* mono/mono@43409aab03 [2019-02] Fix Directory.GetLogicalDrives () (#13286)
* mono/mono@c3b2368aff [mini] Inline Selector.GetHandle for tvOS and watchOS assemblies as well. (#13254)
* mono/mono@ce536b347b [2019-02] [aot] add wrappers to \u0022slim\u0022 mscorlib (i.e. --aot=interp) (#13168)
* mono/mono@5c6441aca8 [interp] compute size of generic valuetype correctly (#13226)
* mono/mono@6ad7d7987d [sdks] Use throttle() instead of lock()
* mono/mono@b5a53bf43a Revert "[sdks] Make sure to run only one build per type per node"
* mono/mono@9ec28a5cdf [ci] Add node name to log of Jenkins pipeline builds
* mono/mono@0d60209c63 [2019-02] [System.Net.Http] Move NSUrlSessionHandler from xamarin-macios to mono (#13249)
* mono/mono@66a15f77b3 [2019-02] [monodroid] Use CoreFX to implement System.Drawing types that used to be in Mono.Android.dll (#13237)
* mono/mono@5fc4dc076d [android] Fix inaccurate detection of sendfile()
* mono/mono@a342f2e4af Bump corefx for type forwarders ported from 2018-10 Xamarin.Android integration
* mono/mono@0aac8c4e0f [2019-02]  Fix multiple issues with response file option on Windows. (#13176)
* mono/mono@077ca320a8 [aot] use unbox arbitrary trampolines for "slim" mscorlib (#13167)
* mono/mono@f438e1b260 [2019-02] [aot] abort lookup early when a method isn\u0027t available in AOT image (#13178)
* mono/mono@60deb21fd8 [ci] Use dl.internalx.com when building on private Jenkins
* mono/mono@979cf7978b [aot] Resolve profile against compiled assembly (#13156)
* mono/mono@b4f8e8a698 [System] Bump SocketTest.TestSelect1 socket timeout to 1ms (#13152)
* mono/mono@ed72d79eda Bump API snapshot submodule
* mono/mono@39e7d07270 Make `System.dll` internals visible to `Mono.Android`.
* mono/mono@5809340a13 [nuget] Add new versions of System.Net.Http
* mono/mono@48ce16320f [nuget] Add new versions of System.Text.Encoding.CodePages ..
* mono/mono@a3f69d7b21 [sdks] Make sure to run only one build per type per node
* mono/mono@2ba053262f use for loop to access item values and avoid InvalidCastException which occurs because VirtualDirectoryMappingCollection enumerator returns key and it's not expected
* mono/mono@8f9491c094 [loader] Fix off by 1 (netstandard is a framework facade)
* mono/mono@91a7262377 Bump bockbuild for GTK fix
* mono/mono@076b66a58a Bump ikdasm
* mono/mono@5212219db3 [mcs] Remove doc about CAS security
* mono/mono@237e312ff7 Pass X509Certificate2 to the certificate validator. (#13036)
* mono/mono@4c2b149264 Remove leading . from script invocation (#13051)
* mono/mono@1ce836d47d [2019-02] Bump linker submodule to latest master (#13034)
* mono/mono@737f6ae708 Set executable bit for all .sh files in repo
* mono/mono@0c2b8e9f24 Correct access permissions to include "user execute" for run-msbuild.sh. (#13042)
* mono/mono@b9fa0ff807 [bitcode] round up value type size for slot calculation (#13008)
* mono/mono@3ba037bc23 Revert "[Facades] Remove System.Drawing.Primitives from xammac_net_4_5_SUBDIRS"
* mono/mono@99dc534da0 [Facades] Remove System.Drawing.Primitives from xammac_net_4_5_SUBDIRS
* mono/mono@55c62ea399 [2019-02] [sdks] Add mac-{mac32,mac64} targets (#12977)
* mono/mono@e62516b7aa [2019-02] [crash] Add more detailed reporting for exceptions (#13000)
* mono/mono@143e2151e6 [System.Net.Http] Improve HttpClientTest to use the retry http listener (#13003)
* mono/mono@5c66a3da2f [2019-02] [ci] Fix Linux x64 Bitcode job (#13004)
* mono/mono@5c6e79ffa7 Mono.Native: Simplify checking for min-version
* mono/mono@1f1942c356 [corlib] Fix CustomAttributeDataTest.MethodIncludesDllImportAttributeData() on watch/tv
* mono/mono@7c3abd8e0d [2019-02] [debugger] Reverting part of https://github.com/mono/mono/pull/12114  (#12960)
* mono/mono@f7f0580b04 [2019-02] [ios] add crosswatch64_32 target (#12939)
* mono/mono@4da62d4568 [2019-02] Bump cecil submodule (#12942)
* mono/mono@d1bab8193b Update roslyn-binaries submodule to point to latest master revision
* mono/mono@f3bdb526f0 Fix issue where togglerefs might be incorrectly pinned. (#12815)
* mono/mono@fc80faabb0 [ci] Bump bockbuild to get fontconfig download url fix
* mono/mono@1790e8a88f [aot] interp flag on AOT images only on mscorlib required (#12891)
* mono/mono@765166c97a [interp] Fix ldelema (#12929)
* mono/mono@14c5f6cc41 [2019-02] [interp] Add method to seq_points table after we finish registering it (#12908)
* mono/mono@6ad34f458f [arm/bitcode] mark valuetype returns as such when dealing with pinvokes (#12912)
* mono/mono@7f5125179d [ci] Support building the OSX .pkg on private Jenkins
* mono/mono@062e05b4f7 Merge pull request #12860 from monojenkins/backport-pr-12856-to-2019-02
* mono/mono@9f6ad1ef7a FIxing crash where a generic enum is passed into get_shared_type. Also added automated test to catch this scenario. (#12848)
* mono/mono@f218806bf3 [2019-02] [metadata] Fix dynamic delegate (#12812)
* mono/mono@e9c6379247 [2019-02] [arm64] encode offset within stack slot for r4 in gsharedvt descriptor (#12887)
* mono/mono@77b48ca726 [sre] Handle null values in MarshalAsAttribute CustomAttributeBuilder
* mono/mono@1dcd313412 [runtime] Use temp folders for merp tests (#12870)
* mono/mono@6abff04d78 [2019-02] [ios] pass --enable-monotouch to cross compilers so icall defintions are visible to it (#12836)
* mono/mono@3101d1c7fb [Registry] Prevent crash due to background thread facing problems in the file system
* mono/mono@35aea5b0ef [tests] Disable flaky block_guard_restore_aligment_on_exit.exe on Windows PRs
* mono/mono@034f1d68a3 [2019-02] Add support for async-streams (C# 8.0). (#12832)
* mono/mono@fd9b8567d5 [2019-02] [corlib] Remove reflection-based Mono.Native test (#12828)
* mono/mono@ea3ee83061 [2019-02] Extend mono-native minimum version magic to CPPFLAGS/CXXFLAGS (#12813)

Diff: 6fe4c149ee...c8906bed28

external/mono

@@ -1 +1 @@
-Subproject commit 6fe4c149ee6b49922a8bcbe80addb685e5ab75f7
+Subproject commit c8906bed284747c2622ecd0ea324fd4463365794