set PKG_CONFIG_PATH to the local opam prefix (to find libminios)
and also remove detection of OCaml 4.00.1 from the config script
Remove support for the 4.00.1 runtime, and only support 4.01.0

There are a growing number of 4.01.0-only libraries, and packaging
on most distributions has improved now such that it's reasonable
to require 4.01.0 only.  We also need to prepare for 4.02.0 soon,
and there's no way we can support three concurrent versions of the
compiler.
Fixes for compiling on ARM
Hacks for compiling on ARM
Hack: Replaced Xen checksum code with Unix version

The Xen version does unaligned double-word accesses, which fault on ARM.