Bug#31745 - crash handler does not work on Windows

- Replace per-thread signal()'s with  SetUnhandledExceptionFilter(). 
  The only remaining signal() is for SIGABRT (default abort()
  handler in VS2005 is broken, i.e removes user exception filter)
- remove MessageBox()'es  from error handling code
- Windows port for print_stacktrace() and write_core() 
- Cleanup, removed some unused functions

sql/sql_parse.cc

@@ -98,22 +98,7 @@ static bool do_command(THD *thd);
 #endif // EMBEDDED_LIBRARY
 
 #ifdef __WIN__
-static void  test_signal(int sig_ptr)
-{
-#if !defined( DBUG_OFF)
-  MessageBox(NULL,"Test signal","DBUG",MB_OK);
-#endif
-#if defined(OS2)
-  fprintf(stderr, "Test signal %d\n", sig_ptr);
-  fflush(stderr);
-#endif
-}
-static void init_signals(void)
-{
-  int signals[7] = {SIGINT,SIGILL,SIGFPE,SIGSEGV,SIGTERM,SIGBREAK,SIGABRT } ;
-  for (int i=0 ; i < 7 ; i++)
-    signal( signals[i], test_signal) ;
-}
+extern void win_install_sigabrt_handler(void);
 #endif
 
 static void unlock_locked_tables(THD *thd)
@@ -1124,7 +1109,7 @@ pthread_handler_t handle_one_connection(void *arg)
   /* now that we've called my_thread_init(), it is safe to call DBUG_* */
 
 #if defined(__WIN__)
-  init_signals();
+  win_install_sigabrt_handler();
 #elif !defined(OS2) && !defined(__NETWARE__)
   sigset_t set;
   VOID(sigemptyset(&set));			// Get mask in use