Enable [CCFileUtils removeSuffixFromFile:] on Mac.

I tried out the new CCFileUtils features on Mac by putting this line in my app delegate:

```objective-c
[[CCFileUtils sharedFileUtils].suffixesDict setObject:@"-hd" forKey:kCCFileUtilsMac];
```

It crashed; long story short, the CCSpriteFrame was referencing the full texture path with suffix, whereas normally it is cached without the suffix. So the texture was being loaded twice. On iPhone the removeSuffixFromFile: function resolves this issue. Unless there's some side-effect I haven't thought of, it should be the same on Mac.