removed old code that moved cache files to new location
removed unused emit() methods from XML classes
EXTRA_LIBS is not used anymore
Don't override CXXFLAGS in configure script

Breaks standard things like:

     make CXXFLAGS="-g -O0 -pg"
Don't override CPPFLAGS and LDFLAGS in configure

For the same reasons as the previous commit
merged branch 'misc_build_fixes' of https://github.com/khaledhosny/dvisvgm
link tests against FreeType library