Fix Windows build issues for librsloader.

This change adds some unimplemented versions of functions from the
mman.h header file (mmap, munmap, mprotect, ...). These functions
are unused on Windows, since we don't actually need the loader.

Change-Id: I2058aa28af43ea2b2d9df77a457928788e2b9f15
Merge tag android-4.3.1_r1 into dev-mips-jb-mr2