[cairo] Makefile.win32 contains recursive definition

[Damian Frank]

src/Makefile.win32 is broken:
C:\cygwin\home\damianf\cairo-build\cairo>make -f Makefile.win32 CFG=release
making all in src...
make[1]: Entering directory `/home/damianf/cairo-build/cairo/src'
Makefile.win32:26: *** Recursive variable `enabled_cairo_headers'
references itself (eventually).  Stop.
make[1]: Leaving directory `/home/damianf/cairo-build/cairo/src'
make: *** [cairo] Error 1

This is true.  Looking at Makefile.win32:
cairo_headers = \
	$(enabled_cairo_headers) \
	$(NULL)

In Makefile.win32.config:
enabled_cairo_headers = $(cairo_headers)

I'm not sure what the fix for this is, but one of these is jumbled.  :-)

Damian