Using named parameters for these is overdue. Passing the session in a
parameter instead of passing username and IP separately will later allow
storing other session info, like username or part of the email.
Note that these functions are not part of the exported API,
and the prototype change will catch (most) skew, so I am not changing
API versions. Any third-party plugins that call them will need updated
though.
* 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.