MFC r209605

MFC r209605
  Improve bufdone_finish()'s handling of the bogus page.  Specifically, if
  one or more mappings to the bogus page must be replaced, call pmap_qenter()
  just once.  Previously, pmap_qenter() was called for each mapping to the
  bogus page.

MFC r209902
  Change the implementation of vm_hold_free_pages() so that it performs at
  most one call to pmap_qremove(), and thus one TLB shootdown, instead of one
  call and TLB shootdown per page.

  Simplify the interface to vm_hold_free_pages().

git-svn-id: svn://svn.freebsd.org/base/stable/8@213890 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f