Self-contained pthread_spinlock_t for RTEMS

Turn pthread_spinlock_t into a self-contained object.  On uni-processor
configurations, interrupts are disabled in the lock/trylock operations
and the previous interrupt status is restored in the corresponding
unlock operations.  On SMP configurations, a ticket lock is a acquired
and released in addition.

See also:

https://devel.rtems.org/ticket/2674

This implementation is simple and efficient.  However, this test case of
the Linux Test Project would fail due to call of printf() and sleep()
during spin lock ownership:

https://github.com/linux-test-project/ltp/blob/master/testcases/open_posix_testsuite/conformance/interfaces/pthread_spin_lock/1-2.c

Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>

newlib/libc/sys/rtems/include/sys/_pthreadtypes.h

@@ -22,6 +22,7 @@
 
 #include <sys/sched.h>
 #include <sys/cpuset.h>
+#include <sys/lock.h>
 
 /*
  *  2.5 Primitive System Data Types,  P1003.1c/D10, p. 19.
@@ -190,7 +191,10 @@ typedef struct {
 /* POSIX Spin Lock Types */
 
 #if defined(_POSIX_SPIN_LOCKS)
-typedef __uint32_t pthread_spinlock_t;        /* POSIX Spin Lock Object */
+typedef struct {
+  struct _Ticket_lock_Control _Lock;
+  __uint32_t                  _interrupt_state;
+} pthread_spinlock_t;                        /* POSIX Spin Lock Object */
 #endif /* defined(_POSIX_SPIN_LOCKS) */
 
 /* POSIX Reader/Writer Lock Types */