drop 'time' dependency

drop 'time' dependency

We're using a very old version of it and the functions we
actually use are available in glibc anyway.

The only difference I found was that the result of
glibc's `strptime()`'s `%s` does *not* want an additional
`.to_local()` call anymore...

... which was weird anyway.

As a minor optimization I pass the format string as `&CStr`
to avoid the memcpy.

(The CString::new() call in `strptime()` only happens during
parameter parsing)

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Reviewed-By: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-By: Stoiko Ivanov <s.ivanov@proxmox.com>
[dropped left-over and fixed FIXME]
Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>