add test for a debug type
add function for finding our CMPs.

much simpler now, since we don't have to look at arguments.
symbolic exec: implement a 'local var' type.

for tracking when a register is loaded with the address of a local
variable.  the actual/real address of the variable is useless
because the debug information stores it relative to the frame
pointer as well, so we need to record that relation.
implement a pretty printer for the register file.

mimics linux kernel oops format.
symbolic exec: fix bug recording RIP-relative addrs

it is relative to the RIP value at the instruction *after* the
current instruction, not the current instruction.
split type signedness test into its own fqn.
testprograms: don't inline 'clamp'.

makes the control flow graphs so much smaller/simpler/nicer.