MSVC 2017 headers aren't warning free at the -Wall level.
Since PSM enables -Wall in some moz.build files, this breaks
--enable-warnings-as-errors builds.
As a temporary measure, disable enough warnings to get working builds.
MozReview-Commit-ID: G0oUsAYYct2
--HG--
extra : rebase_source : dc37783c89e66a54510c9940f9eaa5a4340ef43e
The patch removes 455 occurrences of FAIL_ON_WARNINGS from moz.build files, and
adds 78 instances of ALLOW_COMPILER_WARNINGS. About half of those 78 are in
code we control and which should be removable with a little effort.
--HG--
extra : rebase_source : 82e3387abfbd5f1471e953961d301d3d97ed2973