add or1k (OpenRISC 1000) architecture port

With the exception of a fenv implementation, the port is fully featured.
The port has been tested in or1ksim, the golden reference functional
simulator for OpenRISC 1000.
It passes all libc-test tests (except the math tests that
requires a fenv implementation).

The port assumes an or1k implementation that has support for
atomic instructions (l.lwa/l.swa).

Although it passes all the libc-test tests, the port is still
in an experimental state, and has yet experienced very little
'real-world' use.
diff --git a/configure b/configure
index 7436210..673d291 100755
--- a/configure
+++ b/configure
@@ -250,6 +250,7 @@
 x86_64*) ARCH=x86_64 ;;
 mips*) ARCH=mips ;;
 microblaze*) ARCH=microblaze ;;
+or1k*) ARCH=or1k ;;
 powerpc*) ARCH=powerpc ;;
 sh[1-9bel-]*|sh|superh*) ARCH=sh ;;
 unknown) fail "$0: unable to detect target arch; try $0 --target=..." ;;