man: Add a timespec(3bsd) alias to timeval(3bsd)

Even though man-pages project now includes man pages for system data
types, we still include these for any other system that does not have
them, to provide a self-contained project with code and documentation.
1 job for master in 59 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #6295110
test

00:00:59