Build fix for getopt.h on Apple. (Thanks to Adam Vandenberg for the fix)

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@978 fdac6126-5c0c-442c-9429-916003d36597

src/OpenMesh/Tools/Utils/getopt.h

@@ -20,6 +20,9 @@ OPENMESHDLLEXPORT extern int getopt(int nargc, char * const *nargv, const char *
   }
 
   #endif
+
+#elif defined __APPLE__
+ #include <unistd.h>
 #else
  #include <getopt.h>
 #endif