[LyX/master] Fix build on FreeBSD.

[Enrico Forestieri]

commit 4342411297de880ddd4c950c45b91258c78b8635
Author: Enrico Forestieri <for...@lyx.org>
Date:   Wed Jul 16 22:25:49 2014 +0200

    Fix build on FreeBSD.
    
    Notified by Raphael Kubo da Costa.

diff --git a/src/support/os_unix.cpp b/src/support/os_unix.cpp
index b298a7d..2635d67 100644
--- a/src/support/os_unix.cpp
+++ b/src/support/os_unix.cpp
@@ -23,6 +23,7 @@
 #include "support/lassert.h"
 
 #include <limits.h>
+#include <locale.h>
 #include <stdlib.h>
 
 #ifdef __APPLE__