Update .clang-format file to support break after return type.

This depends on having a recently built version of clang-format
installed, as the patch to support this behavior was only just
recently added to clang-format.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@256526 91177308-0d34-0410-b5e6-96231b3b80d8

.clang-format

@@ -2,7 +2,7 @@ BasedOnStyle: LLVM
 IndentWidth:     4
 ColumnLimit:     120
 BreakBeforeBraces: Allman
-AlwaysBreakAfterDefinitionReturnType: true
+AlwaysBreakAfterReturnType: All
 AllowShortFunctionsOnASingleLine: Inline
 ConstructorInitializerAllOnOneLineOrOnePerLine: true
 IndentCaseLabels: true