Fix minor build problems related to MinGW64.

 configure.ac: Read $srcdir/nt/mingw-cfg.site when $MSYSTEM is
 "MINGW64" as well.

 nt/inc/ms-w32.h (pthread_sigmask): Undefine if defined, for MinGW64.

 src/unexw32.c (_start) [__MINGW64__]: Define to __start.

2 files changed, 9 insertions, 0 deletions

diff --git a/nt/ChangeLog b/nt/ChangeLog
index 52582532fb3..551b973b016 100644
--- a/nt/ChangeLog
+++ b/nt/ChangeLog
@@ -1,3 +1,7 @@
+2014-01-11  Fabrice Popineau  <fabrice.popineau@supelec.fr>
+
+        * inc/ms-w32.h (pthread_sigmask): Undefine if defined, for MinGW64.
+
 2013-12-31  Fabrice Popineau  <fabrice.popineau@supelec.fr>
 
         * inc/ms-w32.h (sys_kill): Fix prototype.
diff --git a/nt/inc/ms-w32.h b/nt/inc/ms-w32.h
index 7f523cb74f9..dca3476b2b6 100644
--- a/nt/inc/ms-w32.h
+++ b/nt/inc/ms-w32.h
@@ -388,6 +388,11 @@ extern int sigemptyset (sigset_t *);
 extern int sigaddset (sigset_t *, int);
 extern int sigfillset (sigset_t *);
 extern int sigprocmask (int, const sigset_t *, sigset_t *);
+/* MinGW64 defines pthread_sigmask as zero in its pthread_signal.h
+   header, but we have an implementation for that function in w32proc.c.  */
+#ifdef pthread_sigmask
+#undef pthread_sigmask
+#endif
 extern int pthread_sigmask (int, const sigset_t *, sigset_t *);
 extern int sigismember (const sigset_t *, int);
 extern int setpgrp (int, int);