Fix mozilla autoconf check : AC_PATH_PROGS() was used incorrectly, and the...

Fix mozilla autoconf check : AC_PATH_PROGS() was used incorrectly, and the check wouldn't error if {mozilla,seamonkey}-config or xulrunner wasn't found

configure.ac

@@ -5650,8 +5650,8 @@ then
           [
             AC_PATH_PROGS(MOZILLA_CONFIG,
 	    [mozilla-config seamonkey-config xulrunner-config],
-            AC_MSG_ERROR([Please install the Mozilla development tools. mozilla-config was not found.])
-		  )
+        [no])
+            test "${MOZILLA_CONFIG}" = "no" && AC_MSG_ERROR([Please install the Mozilla development tools. mozilla-config was not found.])
           ]
         )
     dnl pkg-config failed but we might have found a mozilla-config