DESC
remap_file_pages protection support: avoid lookup of pages for PROT_NONE remapping
EDESC
From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

This optimization avoid looking up pages for PROT_NONE mappings. The idea was
taken from the "wrong "historical" code for review - 1" one (the next one)
from mingo, but I fixed it, by adding another "detail" parameter. I've also
fixed the other callers to clear this parameter, and fixed madvise_dontneed()
to use memset(0) on its parameter - currently it's probably a bug.

Not even-compile tested, just written off the top of my head.
