Rewrite of d_netfil.c's findfile
This branch rewrites findfile
from d_netfil.c
so it'll be able to properly report in Linux and the like whether there was a file found in one of its three search paths with a bad MD5, rather than pretending it doesn't exist.
Note: Untested as of writing, but I assume it should be safe for master, since file searching is entirely local. Could be wrong though.