[cairo] [patch] caching, glyph, font, and glyphset patch, round 2

[graydon hoare]

hi,

here is round 2 of my big font overhaul patch:

  http://people.redhat.com/graydon/cairo-caches-oct-07-2004.patch

I've made a number of corrections based on received feedback (and 
omitted some, not because I necessarily disagree with them but because 
it seems like they can be addressed incrementally, later, when we have 
more experience). the changes since last time are:

  - cairo_font_t has a scale factor stored in it, and a reference
    to a cairo_unscaled_font_t. when you get cairo_current_font
    you get "the current font at the current scale", which you can
    hold on to and re-install in the future. this means that there
    are actually zero changes to cairo.h, with this patch.

  - gone is the stuff related to points and DPI. a font begins as a
    1-user-unit object, and has its device size set by composing the
    scale matrix and CTM. nothing else.

  - the generic cache is rewritten to crib much more extensively from
    keith's other code, in particular xserver/render/glyph.c. it
    uses less memory, involves fewer backend functions, and performs
    better.

hopefully this fixes the most violent objections. may I commit it?

-graydon