gdb patch take 4

* gdb/win32-nat.c
(handle_exception,get_child_debug_event,_initialize_inftarg) When debugging
a program that uses windows SEH gdb stops the program even if the inferior's
exception handler catches the exception.  I have added a new set option,
"set mapexceptionstosignals off" that will cause gdb to completely ignore
WIN32 exceptions. This is similar to the feature "set signal-exceptions 4"
in the Apple Openstep version of gdb 4.15.3.


This patch is relative to gdb-5.2.1-1 from mingw.org.