[RP] Introducting :set timefmt

[Christian Koch]

Hello all,

I'm maintaining my own branch of the ratpoison repo, and I just
implemented some functionality others might be interested in.

It's a new variable for the :set command, called ``timefmt''. This is a
string used to format the appearance of the output of the :time command,
and it works just like strftime(). The default value emulates the output
of ctime(), which is what the ``canonical'' ratpoison uses.

You can see the relevant changes here:

https://github.com/christiank/ratpoison/commit/f3f4dd2157f015e0b39cd5816ef72a5f3fb5ad3b

https://github.com/christiank/ratpoison/commit/9b7f5a5628208d58fb6c46bf106a792eb2021e35

https://github.com/christiank/ratpoison/commit/f4eea30db9462850ac9bbba6d81c30579036de5d

-Christian