* Makefile.in: Remove cygserver stuff.

* acconfig.h: Add USE_CYGSERVER define.
* config.h.in: Regenerate.
* configure.in: Add --enable-server setting.
* configure: Regenerate.
* fhandler_tty.cc (fhandler_tty_slave::open): Conditionalize compilation of
cygserver stuff.
* fork.cc (fork_child): Ditto.
* shm.cc: Ditto.
* tty.cc (tty::common_init): Ditto.
* dcrt0.cc: Use bool rather than BOOL for CYGWIN environment variable
definitions.
* environ.cc: Ditto.
* ntea.cc: Ditto.
* security.cc: Ditto.
* security.h: Ditto.
* syscalls.cc (check_posix_perm): Remove externs that were already declared in
a header.
* winsup.h: Ditto.  Declare _MT_SAFE here.  Delete it someday since cygwin
should always be _MT_SAFE.

winsup/cygwin/fork.cc

@@ -298,8 +298,10 @@ fork_child (HANDLE& hParent, dll *&first_dll, bool& load_dlls)
   (void) ForceCloseHandle1 (fork_info->subproc_ready, subproc_ready);
   (void) ForceCloseHandle1 (fork_info->forker_finished, forker_finished);
 
+#ifdef USE_CYGSERVER
   if (fixup_shms_after_fork ())
     api_fatal ("recreate_shm areas after fork failed");
+#endif
 
   pinfo_fixup_after_fork ();
   signal_fixup_after_fork ();