Add class udpmcastsender.
 Add sdebug.h for debug macros.

 Changes to be committed:
	modified:   Makefile
	modified:   inetinterface.h
	new file:   mcastsend_test.cpp
	new file:   sdebug.h
	new file:   udpmcastsender.cpp
	new file:   udpmcastsender.h
	modified:   wall.cpp
	modified:   wand.cpp