Adjust for microtime() ABI on all XBSD

On the BSDs, struct timeval is not two 32-bit integers like our
struct clock, so the ABI is quite incompatible.  Use the native type
for the function call and translate to our local type accordingly.

Unlike on master, there was no workaround in the FreeBSD kernel build
to remove.

Reviewed-on: http://gerrit.openafs.org/10340
Reviewed-by: Jeffrey Hutzelman <jhutz@cmu.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Antoine Verheijen <apv@ualberta.ca>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 1bdcc3c7bca092f189f434f1f7b174090c24250c)

Change-Id: I54cb609f80bc35fb09a5026c964ba28ae860f3f5
Reviewed-on: http://gerrit.openafs.org/10374
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>