Modify the build system and the source
files to support building a CLI-only
version with only glib2 as a dependency.
Use CLI_ONLY=1 ./configure, then make clean all.
Remove build.h and version.tex from versioning, they're autogenerated
Make 'Makefile' the dummy makefile to instruct user to launch configure if no GNUmakefile is found
Make GNUmakefile the generated makefile and exclude it from the versioning
Update .gitignore accordingly