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/signal.h

@@ -0,0 +1,80 @@
+#if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
+ || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+
+#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+typedef unsigned long greg_t, gregset_t[34];
+typedef struct sigcontext {
+	struct {
+		unsigned long gpr[32];
+		unsigned long pc;
+		unsigned long sr;
+	} regs;
+	unsigned long oldmask;
+} mcontext_t;
+#else
+typedef struct {
+	unsigned long __regs[35];
+} mcontext_t;
+#endif
+
+struct sigaltstack {
+	void *ss_sp;
+	int ss_flags;
+	size_t ss_size;
+};
+
+typedef struct __ucontext {
+	unsigned long uc_flags;
+	struct __ucontext *uc_link;
+	stack_t uc_stack;
+	mcontext_t uc_mcontext;
+	sigset_t uc_sigmask;
+} ucontext_t;
+
+#define SA_NOCLDSTOP  1
+#define SA_NOCLDWAIT  2
+#define SA_SIGINFO    4
+#define SA_ONSTACK    0x08000000
+#define SA_RESTART    0x10000000
+#define SA_NODEFER    0x40000000
+#define SA_RESETHAND  0x80000000
+#define SA_RESTORER   0x04000000
+
+#endif
+
+#define SIGHUP    1
+#define SIGINT    2
+#define SIGQUIT   3
+#define SIGILL    4
+#define SIGTRAP   5
+#define SIGABRT   6
+#define SIGIOT    SIGABRT
+#define SIGBUS    7
+#define SIGFPE    8
+#define SIGKILL   9
+#define SIGUSR1   10
+#define SIGSEGV   11
+#define SIGUSR2   12
+#define SIGPIPE   13
+#define SIGALRM   14
+#define SIGTERM   15
+#define SIGSTKFLT 16
+#define SIGCHLD   17
+#define SIGCONT   18
+#define SIGSTOP   19
+#define SIGTSTP   20
+#define SIGTTIN   21
+#define SIGTTOU   22
+#define SIGURG    23
+#define SIGXCPU   24
+#define SIGXFSZ   25
+#define SIGVTALRM 26
+#define SIGPROF   27
+#define SIGWINCH  28
+#define SIGIO     29
+#define SIGPOLL   29
+#define SIGPWR    30
+#define SIGSYS    31
+#define SIGUNUSED SIGSYS
+
+#define _NSIG 65