Fix Win32 GC_write preventing potential infinite recursion at abort

Fix Win32 GC_write preventing potential infinite recursion at abort

* misc.c (GC_write): Define "inside_write" static variable (only
for Win32 and only if THREADS and GC_ASSERTIONS or
GC_PRINT_VERBOSE_STATS); if this variable is set then just return,
set this variable if GC_write_disabled or GC_log is
INVALID_HANDLE_VALUE just before ABORT call (to prevent infinite
recursion).
* misc.c (GC_default_on_abort): Do not call WRITE if GC_write_disabled
(only for Win32 and only if THREADS and GC_ASSERTIONS) to prevent
abort in GC_write.