timer: restore PRETRANSFER timing

Regression introduced in 7.23.0 with commit 9dd85bce. The function in
which the PRETRANSFER time stamp was recorded was moved in time causing
it be stored very quickly after the start timestamp. On most systems
shorter than 1 millisecond and thus it wouldn't even show with -w
"%{time_pretransfer}" using the command line tool.

Bug: http://curl.haxx.se/mail/archive-2011-12/0022.html
Reported by: Toni Moreno