Merge pull request matplotlib#1272 from dmcdougall/mac_objc1

Fix Objective-C 2.0 error with gcc-4.0

Author: efiring

src/_macosx.m

@@ -5769,7 +5769,10 @@ - (int)index
     if(nwin > 0)
     {
         [NSApp activateIgnoringOtherApps: YES];
-        for (NSWindow *window in [NSApp windows]) {
+        NSArray *windowsArray = [NSApp windows];
+        NSEnumerator *enumerator = [windowsArray objectEnumerator];
+        NSWindow *window;
+        while ((window = [enumerator nextObject])) {
             [window orderFront:nil];
         }
         [NSApp run];