Thread IDs are now symbolic but something goes wrong later on!
--debug-print-instructions is now more readable with '\n' appended.
Added capability to klee-control to switch printing of instructions
on/off
fix trailing spaces on end of lines.
Found potential bug in race detection. Not sure yet, have commented and
will fix soon.
A symbolic Thread ID is now stored in the Thread Class (to be used
for race checking later).