[cairo] Decoupling win32-surface and win32-font

[Behdad Esfahbod]

So, similar to the recent discussion about quartz and atsui, I want to
see it possible to use win32-font with non-win32 backends and vice
versa.  The case of win32-surface without win32-font should already
work.  win32-font needs some fixes to not assume win32-surfaces though.
Should be easy to fix for 1.4.2.

What may not be easy to fix later however is the fact that there is no
cairo-win32-font.h and those functions are put in cairo-win32.h.  For
the least, I want to suggest that we wrap them with #if
CAIRO_HAS_WIN32_FONT correctly.  Or better, add a new header,
cairo-win32-font.h, and have cairo-win32.h include it for backward
compatibility.

Thoughts?

(in the same line, we still need to fix xlib compilation without ft and
render, but I'm only concerned about public API right now.)

-- 
behdad
http://behdad.org/

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