[FT2 Status] Cache Subsystem available

[David Turner]

Hello,

  I have added a new caching sub-system for FreeType 2 in "src/cache".
  You can read the API in <freetype/ftcache.h>

  NOTE THAT THE CODE COMPILES WELL, BUT HASN'T BE TESTED YET. IT
  WILL MOST CERTAINLY CRASH OR NOT FUNCTION PROPERLY

  Basically, the sub-system provides you the following capabilites:

    1. caching FT_Face & FT_Size objects, through a "cache manager":

       the manager doesn't force you to install/list fonts on the system
       in a specific way. Rather, client applications must provide a
       callback that is used to translate abstract "face IDs" into
       real FT_Face objects when needed.


    2. caching individual glyph images, through an "image cache":

       this object is capable of holding individual glyph images in
       very different formats, while limiting the total amount of
       memory taken by the glyphs. It can hold images in these
       formats:

          - monochrome bitmaps
          - anti-aliased bitmaps
          - vector outlines
          - original (unscaled) master outlines

       other formats should be trivial to add. The image cache returns
       "FT_Glyph" objects.

    It should be possible to add a "metrics cache" of "kerning cache"
    to the sub-system later in the future.

For now, I'm going to test the code extensively and let you know when it
is ready for prime time. Meanwhile, please have a look at the API and
dare to comment it :-)

Cheers,

- David