Missing increment of vacrelstats->pinskipped_pages

lazy_vacuum_heap() does not count pages that it skips due to not 
obtaining the buffer cleanup lock. vacuum_pinskipped.patch fixes that. 
That should be backpatched to 9.5.

vacuum_comment.patch cleans up a comment in lazy_scan_heap().
-- 
Jim C. Nasby, Data Architect                       jim@nasby.net
512.569.9461 (cell)                         http://jim.nasby.net