Add OpenRISC support

This patch adds support for the OpenRISC architecture.
(http://opencores.org/or1k/Main_Page)

This patch has been tested under Linux with QEMU-user emulation support.
- 32 Bit
- big endian
- delayed instructions
This is the only available configuration under Linux.

The description of the ABI can be found on the official website.

Is passes the testsuite except of the unwindtest_ffi_call.cc
testcase, which seems to be a problem of gcc and not libffi.
Some testcases of the gcc testsuite still fail.

Signed-off-by: Sebastian Macke <sebastian@macke.de>