[corlib] Update CurrentRegion to work with DefaultThreadCurrentCulture
Remove some more mdb bits.
[corlib] CreateSpecificCulture without exception retry
Unbreak libgc.
Merge pull request #824 from hanswolff/patch-1

Fixed missing pointer conversion tests in sizes.c
Fix a warning on PPC.
Fix more PPC warnings.
Fix a couple of warnings in mini-exceptions.c.
Fix some warnings in mini-amd64.c.
[corlib] Better conversion betwen system locale and CultureInfo. Fixes #15875
Fix some warnings caused by always_inline functions not being marked inline.
Add a dummy assignment to shut GCC up.
Fix some pointer/integer size issues in unwind.c on 32-bit systems.
[xbuild]: Fix the tests.

'TestMessageLogger.Count' should not be used in tests to check for the
number of logged messages because it would also includes diagnostic messages.

Extra diagnostic messages should not be considered an error condition; in
fact, we have too few diagnostic messages, not too many.

Use 'TestMessageLogger.NormalMessageCount' and 'TestMessageLogger.WarningMessageCount'
instead.
Fix some warnings in mini-arm.c.
Apply __builtin_extract_return_addr to the result of __builtin_return_address.
Also use __builtin_extract_return_addr in these files.
Fix the windows build.
Fix the pp64 build.
Fix monograph to build under various --disable-boehm/--disable-libraries configurations.