Debugging flags for the SR runtime system

Flag values are used in the DEBUG macro.
Debugging is enabled by "setenv SRXDEBUG hexvalue".

    000F -- miscellaneous
	1	srx inputs
	2	srx actions
	4	clock events
	8	resource termination
    00F0 -- sockets
	10	packets sent
	20	packets received
	40	misc socket I/O
	80	select() calls
    0F00 -- processes
	100	activate
	200	block
	400	spawn, kill
	800	restart (context switch)
    F000 -- semaphores
	1000	V
	2000	P
	4000	create
	8000	destroy
    F0000 -- dynamic memory allocation
	10000	new/free calls
	20000	talloc calls
	40000	low-level allocation
