Default to using CoreText renderer

The default renderer is too "loose" on OS X 10.8 whereas the CoreText
renderer looks the same across all platforms.  Furthermore, the CoreText
renderer is many times faster.

A downside to the CoreText renderer is that it does not support the text
input protocols properly, so e.g. three-finger tapping to show
dictionary results does not work.  It also does not show marked text as
it is being drawn if the "inline marked text" option is disabled.

src/MacVim/MMAppController.m

@@ -207,7 +207,7 @@ + (void)initialize
         [NSNumber numberWithInt:0],     MMOpenInCurrentWindowKey,
         [NSNumber numberWithBool:NO],   MMNoFontSubstitutionKey,
         [NSNumber numberWithBool:YES],  MMLoginShellKey,
-        [NSNumber numberWithInt:0],     MMRendererKey,
+        [NSNumber numberWithInt:2],     MMRendererKey,
         [NSNumber numberWithInt:MMUntitledWindowAlways],
                                         MMUntitledWindowKey,
         [NSNumber numberWithBool:NO],   MMTexturedWindowKey,