- add debug domains which enable multiple debugging statements
  collectively
- add a debug domain DEBUG_ALL which enables all debugging messages
- print the debug domain in the debug message
- add some debug statements
- enable some domains

To print the domain, the debug() macro converts the domain into a
string and adds the value 6 to skip the "DEBUG_" prefix.

It looks like they are too large for the stack.

Use two timestamp tables to distinguish between data and redundancy
packets.

Change sender and receiver to use app-layer packet identifiers. Receiver now terminates after given number of rounds. Targetdelay increased to avoid cleaning problems.

 - Implement PrrtTimestamp data structures and functions
 - Add PrrtTimeStampClock and PrrtTimeStampCycle macros where desired
 - Dump timestamp results to stdout

Conflicts:
	src/prrt/block.h
	src/prrt/packet.c
	src/prrt/processes/data_receiver.c
	src/prrt/processes/data_transmitter.c
	src/prrt/processes/feedback_receiver.c
	src/prrt/socket.c
	src/prrt/socket.h
	src/prrt/stores/forward_packet_table.c
	src/receiver.c
	src/sender.c
	src/util/list.c
	src/util/list.h