Rework the gsharedvt code to add support for vtypes with arbitrary size.
Disable gc-altstack.exe on wrench until it is fixed (#12610).
Fix a typo in e5c45f1161604733b116a0a83782c08f74fb3127.
Fix a couple of warnings in appdomain.c and threads.c.
Eliminate the use of localloc in gsharedvt methods which have no gsharedvt locals.