Fix a problem where CPU time was computed wrong.

This definitely affected FreeBSD, which breaks POSIX.1 by not
setting CLOCKS_PER_SEC to 1000000 (see clock(3)).  At this point
I can't tell if any other platforms were affected by this.

(cherry picked from commit bf219a4d51f6a0d17bb1eca393d978c610f0c114)
Signed-off-by: Bruce A. Mah <bmah@es.net>