Backport of this changeset

http://lists.mysql.com/commits/59686

Cleanup pthread_self(), pthread_create(), pthread_join() implementation on Windows.
Prior implementation is was unnecessarily complicated and even differs in embedded
and non-embedded case.
      
Improvements in this patch:
* pthread_t is now the unique thread ID, instead of HANDLE returned by beginthread
      
This simplifies pthread_self() to be just straight GetCurrentThreadId().
prior it was much  art involved in passing the beginthread() handle from the caller
to the TLS structure in the child thread ( did not work for the main thread of
course)
      
* remove MySQL specific my_thread_init()/my_thread_end() from pthread_create.
No automagic is done on Unix on pthread_create(). Having the same on Windows will 
improve portability and avoid extra #ifdef's
      
* remove redefinition of getpid() - it was defined as GetCurrentThreadId()

sql/sql_connect.cc

@@ -39,10 +39,6 @@
 #define MIN_HANDSHAKE_SIZE      6
 #endif /* HAVE_OPENSSL */
 
-#ifdef __WIN__
-extern void win_install_sigabrt_handler();
-#endif
-
 /*
   Get structure for logging connection data for the current user
 */
@@ -612,13 +608,8 @@ void thd_init_client_charset(THD *thd, uint cs_number)
 bool init_new_connection_handler_thread()
 {
   pthread_detach_this_thread();
-#if defined(__WIN__)
-  win_install_sigabrt_handler();
-#else
-  /* Win32 calls this in pthread_create */
   if (my_thread_init())
     return 1;
-#endif /* __WIN__ */
   return 0;
 }