* malloc.c(GC_free): Ignore bad frees on MSWIN32 with REDIRECT_MALLOC.
* NT_MAKEFILE: msvc_dbg.h is in include/private. Don't use cvars
rc.
* misc.c (WIN32 GC_write): Define GC_need_to_lock in single-threaded
case.
* win32_threads.c: Test for __MINGW32__ in addition to _MINGW_VER.
(GC_CreateThread, GC_beginthreadex): Deallocate args even if we fail.
* include/gc.h: Add GC_reachable_here(). (GC_WinMain): Add GC_API.
(GC_beginthreadex, GC_endthreadex, GC_ExitThread): Declare.
* tests/test.c: Add GC_reachable_here() call.