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.

arch/or1k/bits/fenv.h

@@ -0,0 +1,10 @@
+#define FE_ALL_EXCEPT 0
+#define FE_TONEAREST  0
+
+typedef unsigned long fexcept_t;
+
+typedef struct {
+	unsigned long __cw;
+} fenv_t;
+
+#define FE_DFL_ENV      ((const fenv_t *) -1)