File dialog looks ugly in Mac OS X

[Lauszus]

This commit: 8bcf02a caused the file dialog in Mac OS X to look "ugly".

It looks like it uses a custom one instead of the native file dialog in Mac OS X.

I tried to reverse the commit and then it looked normal again.
See the two screenshots provided below:

This is the old file dialog:

And this is the new one:

[ffissore]

Fixed with e327bb0. Available since next nightly and in 1.6.1