Improving the retrieval of the user's locale on Apple systems.

The previous behavior used the entire local identifier string that includes optional settings such as variant and calendar format. This returns locales like en_US_POSIX@calendar=buddhist which result in the user's culture being the invariant culture.

This change builds the locale from the language, country code and optional script code so that the locale returned is in the expected format.

This commit is licensed under MIT/X11.
Fixed a some compiler warnings
Fix condition (for MOBILE) that excluded System.Xml.Schema/Extensions.cs. Removed the condition since every profile we now support includes this [#15552]
Merge pull request #730 from LogosBible/locale-changes

Improving the retrieval of the user's locale on Apple systems.
[sdb] Add an IncludeSubclasses property to ExceptionEventRequest, to control whenever to include subclasses of the exception type. Fixes #15541
[runtime] Use a cache in mono_create_rgctx_lazy_fetch_trampoline () in the full-aot case as well.
[runtime] Avoid running tests using AC_TRY_RUN () when cross-compiling.
[sdb] Fix support of vtypes passed by ref.
[runtime] Make --regression work when a domain is not yet setup during porting.
[jit] Add a MONO_ARCH_EMULATE_LONG_MUL_OVF_OPTS define for architectures which have mul but not mul.ovf opcodes.
runtime] Print unwind information in the JIT debug output.
[jit] Add a 'call_info' field to MonoCallInst so the OP_CALL_... opcodes have access to the calling convention information computed in mono_arch_emit_call ().
[jit] Add a 'relocation' field to MonoJumpInfo which contains an architecture specific relocation constant so mono_arm_patch_code () doesn't have to decompile the patch site to determine the type of patching to do.
[jit] Add a MONO_TRAMPOLINE_TYPE_HAS_ARG macro which determines whenever a given trampoline type receives its argument directly in a register.
[jit] Add a mini_exception_id_by_name () helper function.
[runtime] Avoid crashing in mini_jit_info_table_find () if the current thread is not set.
[runtime] Add a mono_restore_context () helper function.
[runtime] Fix gsharedvt support in mono_helper_compile_generic_method ().
[runtime] Add a mini_get_nullified_class_init_trampoline () helper function.
[runtime] Use mini_get_nullified_class_init_trampoline () to reduce code duplication in the back ends.