* Mono.Posix.dll.sources: Add Mono.Unix.Native/RealTimeSignum.cs.

	* Mono.Posix.dll.sources: Add Mono.Unix.Native/RealTimeSignum.cs.
	* Mono.Posix_test.dll.sources: Add
	  Mono.Unix.Native/RealTimeSignumTest.cs.
	* Mono.Unix/UnixSignal.cs: Allow RealTimeSignums to be used in addition
	  to Signum, so that real time signals can be used.  Patch thanks to
	  tim.jenks@realtimeworlds.com.
	* Mono.Unix.Native/NativeConvert.cs: Add FromRealTimeSignum(),
	  ToRealTimeSignum().  Patch thanks to tim.jenks@realtimeworlds.com.
	* Mono.Unix.Native/RealTimeSignum.cs: Added; structure which represents a real-time
	  signal, a value V such that V >= SIGRTMIN and V <= SIGRTMAX.
	  Patch thanks to tim.jenks@realtimeworlds.com.
	* Mono.Unix.Native/Stdlib.cs: Add SetSignalAction() and raise()
	  overloads which accept a RealTimeSignum instance.
	  Patch thanks to tim.jenks@realtimeworlds.com.
	* Test/Mono.Unix/UnixSignalTest.cs: Add tests for RealTimeSignum
	  constructors, .RealTimeSignum and .IsRealTimeSignal properties.
	  Patch thanks to tim.jenks@realtimeworlds.com.
	* Test/Mono.Unix.Native/RealTimeSignumTest.cs: Added; unit tests for
	  RealTimeSignum.  Patch thanks to tim.jenks@realtimeworlds.com.

svn path=/trunk/mcs/; revision=121851