Many of Pango's dependencies do not support a build system for Visual
Studio that would generate the pkg-config files for them, so we need to
try to look for them using cc.has_header() and cc.find_library() for
them, namely for Cairo, FreeType, FontConfig and HarfBuzz as fallbacks.

For Cairo, things are more complicated as there are multiple build
options and configurations for it, so we need to check for those that we
need after we find the Cairo headers and libraries by:

-Including the respective headers (for cairo-win32.h, cairo-ps.h,
 cairo-pdf.h, cairo-quartz.h and cairo-xlib.h, since these features
 must have been enabled when Cairo is built and installed in order for
 those headers to be succesfully included)
-For pangocairo with FreeType support, we need to check whether the
 FontConfig support is built into Cairo as well, as FontConfig support
 is actually required in Cairo for this.
-For Cairo/PNG output surface support, check whether Cai...