mod_log_config: instead of using the new dedicated
pattern format "%M" for duration milliseconds,
overload the existing "%D" to choose the time precision
("%{s}D" for seconds, "%{ms}D" for milliseconds and
"%{us}D" for microseconds).

The existing %T and %D without precision are kept for
compatibility.

The previously introduced "%M" (r1677187) is removed,
it has not yet been released. Format pattern characters
are rare, so we should only use a new one if an
existing one isn't a good fit.


Fix syntax.


Follow-up to r1680895:

Let %T be the format character which accepts time resolution
arguments.

Submitted by: rjung, trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1681106 13f79535-47bb-0310-9956-ffa450edef68