Splitting package libfm-dev into libfm-dev and libfm-gtk-dev.

Some of users may never want use gtk libs but only libfm itself and enforce
to install all gtk stuff (libgtk and other dependencies) if it isn't
needed by user is completely wrong, and Debian Policy states that
unneded dependencies are bad.
Splitting package libfm-dbg into libfm-dbg and libfm-gtk-dbg.

Some of users may never want use gtk libs but only libfm itself and enforce
to install all gtk stuff (libgtk and other dependencies) if it isn't
needed by user is completely wrong, and Debian Policy states that
unneded dependencies are bad.