length back to munmap(). Evaluate intersection between given
area and mapped area and return it, if any.
(mmap64): On regular files, don't allow mappings beginning beyond
EOF. Return with errno set to ENXIO instead.
(munmap): Rewrite SUSv3 conformant. Check if given memory area is
valid. Unmap all maps inside given memory area. Don't return error
if no mapping has been unmapped.
f2d3c47b14