NSGlyphGenerator

[Fred Kiefer]

I just commit a big patch that adds the class NSGlyphGenerator and uses 
this instead of direct glyph generation inside of GSLayoutManager.

As this is a very important class and the code here is not that easy I 
would like you all to test that change in the next few days. This new 
implementation will hopefully allow for a very easy way to implement 
secure text fields correctly and allow for other glyph generation 
changes more easily. There is also plenty of space to make this more 
efficient, but first we must be sure it is working correctly.

Cheers,
Fred