Remove unneeded #if defined(HAVE_GMETADOM)

Those files are only compiled when GMetaDOM is enabled anyway.
This define is not needed anymore it seems
Support parsing entities in the libxml2 front end

Fixes #3
Remove unused code
Minor
Remove unused code after a06c0ed
Make the Cairo less Pango-dependant
Remove recently unused code
Include header where it is actually needed
Minor
Move function to its only caller
Added a Cairo shaper that does not depend on Pango
Drop unused Cairo_PangoShaper after 70636fa
Drop the last Pango dependency in Cairo backend
Remove unnecessary includes
Rename COND_ → HAVE_

This seems to be the convention used elsewhere.
Cairo backend no longer depend on Pango
Check for Cairo and Pango independent of GTK
The simple viewer no longer depends on Pango
Remove obsolete item