Add supporting functions for easier timestamping for a 'timing' channel, and
start implementing some of the more important timings to capture.
Track the time from a data connection starts, to when the first byte is
read/written.

Cleaned up the syntax in some of this file, to make for easier
reading/maintenance.
Merge pull request #65 from proftpd/trace-timing-channel-bug4058

Bug#4058 -  Create a 'timing' trace channel, for timing-related data