introduced in amd64 revision 1.540 and i386 revision 1.547. However, it
had no harmful effects until after a recent change, r189698, on amd64.
(In other words, the error is harmless in RELENG_7.)
The error is triggered by the failure to allocate a pv entry for the one
and only mapping in a page table page. I am addressing the error by
changing pmap_copy() to abort if either pv entry allocation or page
table page allocation fails. This is appropriate because the creation of
mappings by pmap_copy() is optional. They are a (possible) optimization,
and not a requirement.
Correct a nearby whitespace error in the i386 pmap_copy().
Crash reported by: jeff@
MFC after: 6 weeks
2553ba9c64