bottle_version: support fontforge scheme.
hexchat: make python an optional dependency.
libstfl: make python an optional dependency.
libtorrent-rasterbar: make python optional.
libxml2: make python an optional dependency.
llvm: make python an optional dependency.
macvim: make python an optional dependency.
postgres-xc: make python an optional dependency.
postgresql: make python an optional dependency.
pyqwt: make python a hard dependency.
pyqwt: set PYTHONPATH in test.
vim: make python an optional dependency.
vte: make python a hard dependency.
vte: add dependency on pygobject.
vte3: make python a hard dependency.