* Rename --getctime to --gettime. (The old name still works for
backwards compatability.)
* --gettime now also looks up last modification time.
* Add rcs_getmtime to plugin API; currently only implemented
for git.
Use mtn for monontone and hg for mercurial. The long names cause ugly
formatting in recentchanges, which has CSS that only allows a few
characters for the commit type column.
Move rcs plugin load to loadplugins; move duplicate rcs detection logic out
of individual plugins and into loadplugins. Avoids checkconfig failing when
run twice.