[cairo] Win32 makefiles patch

[Tor Lillqvist]

Behdad Esfahbod writes:
 > Does the win32 make used with these files support includes?

That would be Microsoft's nmake. (No relation to possibly identically
named Make implementations on Unix). Yes it does, using the syntax

!INCLUDE pathname

 > In that case we should move some of the shared lists of files into
 > a separate .mk file and include it from the .am and .win32 ones.

Excellent idea.

--tml