Revert the reversion and go with implementation described in cgf-000017, with

some modifications.
* init.cc (dll_entry): Revert previous change.
* miscfuncs.cc: Include sigproc.h for exit_thread declaration.
* winsup.h (ExitThread): Define as 'exit_thread' to ensure no accidental use.
* sigproc.cc (exit_thread): New function.
(wait_sig): Handle __SIGTHREADEXIT case.  Don't just block rather than
returning from this function.
* sigproc.h (__SIGTHREADEXIT): New enum.
(exit_thread): Declare.
* sync.cc (muto::release): Accept a tls command-line argument.
* sync.h (muto::release): Accept a tls command-line parameter.  Default to
&_my_tls.
* cygerrno.h (__set_errno): Define as extern so that no function code is ever
emitted.
* cygserver_ipc.h (cygserver_ipc.h): Ditto.
* miscfuncs.h (transform_chars): Ditto.
* path.h (has_attribute): Ditto.
* security.h (privilege_luid): Ditto.
* winsup.h (flush_file_buffers): Ditto.

winsup/cygwin/sigproc.h

@@ -25,7 +25,8 @@ enum
   __SIGHOLD	    = -(NSIG + 7),
   __SIGNOHOLD	    = -(NSIG + 8),
   __SIGEXIT	    = -(NSIG + 9),
-  __SIGSETPGRP	    = -(NSIG + 10)
+  __SIGSETPGRP	    = -(NSIG + 10),
+  __SIGTHREADEXIT   = -(NSIG + 11)
 };
 #endif
 
@@ -87,6 +88,7 @@ void __stdcall sigalloc ();
 
 int kill_pgrp (pid_t, siginfo_t&);
 int killsys (pid_t, int);
+void exit_thread (DWORD) __attribute__ ((regparm (1), noreturn));
 
 extern "C" void sigdelayed ();