Add tests for bug #8468

Conflicts:

	mcs/class/System.XML/Test/System.Xml.Serialization/DeserializeTests.cs
[Mono] TimeZoneInfo.FindSystemTimeZoneById returns null

Fixes: https://bugzilla.xamarin.com/show_bug.cgi?id=7966

If we cannot find the requiested time zone we should throw a
TimeZoneNotFoundException rather than returning null.
Disable LLVM for methods with nested clauses for now to work around #6650.
Disable AOT pretty symbol names on iOS.

	* dwarfwriter.c: Don't emit symbol description on iOS
	as it crashes dsymutil for darwin-ios.
Add macros to sgen meant to replace DEBUG

	* sgen-gc.h: Add log and assertions macros so we can have different logging levels
	for them and so we can better abstract the logging medium.
Replace all uses of DEBUG with SGEN_LOG and SGEN_ASSERT.

	* sgen-*.*: Kill the DEBUG macro in favor of clean alternatives.
Kill explicit usages of gc_debug_file.
Kill sgen_get_logfile and sgen_debug_printf.
Add stdout/stderr wrappers for the gc and runtime.

	* mono-logger-internals.h: Add wrappers that correctly redirect
	to the right place on iOS and Android devices.

	The new functions are line oriented so they don't allow to use multiple
	calls to produce a single line. Callers should re-arrange their code to
	properly handle this as those devices only have line-oriented facilities.
Switch sgen to use utils/mono-logger-internal.h for logging.
Switch exception reporting to use utils/mono-logger-internal.h.
Redirect console output for iOS/Android when tracing.

	* trace.c: Given the quite complex usage of printf by
	the tracing code, we resort to a simple hack to do it.
Redirect g_print and relatives to the device log in MonoTouch.

	* goutput.c: Redirect output to the device log on iOS devices.
Added a workaround for #2190. Avoid calling mono_arch_get_argument_info () from the stack walking code on x86, its not signal safe.
For some unknown reason sequence points on wrappers are disabled on android.
Fixe memberref parent token size calculation.
Optimize OBJ_BITMAP_FOREACH_PTR () using __builtin_ctz ().
Fix OBJ_BITMAP_FOREACH_PTR () for non gcc compilers.
Disable --tls=__thread support when using clang until it is fixed.
Rename 'thread_info' global in sgen to 'sgen_thread_info' since it seems to conflict with a system definition on osx when using clang.