Move more of times into accessors, more modern times.

Move more of times into accessors, more modern times.
Many of the remaining explicit accesses to wpt->microseconds aren't actually
 using it as microseconds at all, but rather as a generic integer. :-(

git-svn-id: http://gpsbabel.googlecode.com/svn/trunk@4399 f51c46e8-681c-474f-0cfe-069cfd0219fb