Make lwp.h always provide fasttime prototypes

Make lwp.h always provide fasttime prototypes

The fasttime functions are used regardles of whether we're using
pthreads or LWP. Previously, lwp.h only provided their prototypes
if LWP was in use. Change this so these prototypes are always provided,
by refactoring the header a little. In the process, remove some
duplicate header includes.

Reviewed-on: http://gerrit.openafs.org/56
Verified-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>