added support for ELF binaries
added support for ELF shared libs via mmap code borrowed from svr4_misc.c
incorporated a few XENIX patches from Andreas Wrede <andreas@planix.com>
to the stat(2) family and msync(2). This uses a primitive function
versioning scheme.
This reverts the libc shared library major version from 13 to 12, and
adds a few new interfaces to bring us to libc version 12.20.
From Frank van der Linden <fvdl@NetBSD.ORG>.