[PATCH] Fix M4 build on DragonFly BSD

[GW]

M4 does not build "as is" on DragonFly BSD. However, the fix we found and used 
for a while at DragonFly is actually fairly simple:


--- lib/fpending.h.orig 2013-11-05 16:23:53.676412000 +0100
+++ lib/fpending.h      2013-11-05 16:25:14.837659000 +0100
@@ -24,6 +24,8 @@
 # include <stdio_ext.h>
 #endif
 
+#ifndef __DragonFly__
 #ifndef __fpending
 size_t __fpending (FILE *);
 #endif
+#endif

This patch is against release 1.4.17 as I was not successful at bootstraping 
against master from a git clone of M4 repository. However, it is fairly simple 
to apply anyway.

DragonFly BSD and pkgsrc teams would be pleased to have this merged into M4 to 
avoid subsequent patching.