INT E0 - PCROBOTS v1.41 - "DEBUG_FLAG" - SET/CLEAR MARKERS NEXT TO ROBOT'S NAME
	AX = 001Dh
	BX = flag number (0 or 1)
	CX = new value (0 reset, 1 set)
Return: nothing
Program: PCROBOTS is P.D. Smith's adaptation of Tom Poindexter's CROBOTS, in
	  which specially-written .COM or .EXE programs form robots battling
	  each other in a user-defined arena
Note:	the two flag markers may be used for any purpose, typically for
	  debugging to provide a visual display of progress