Add stash.[hc] for reading/writing GKeyFile settings and (later)
synchronizing widgets with C variables. Currently this only
supports boolean and integer settings.
Replace keyfile.c SettingEntry code with new stash code.
git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@3285 ea778897-0a13-0410-b9d1-a72fbfd435f5
