move function instructions to a separate header

part of moving all instructions into headers in instruction/*.h
move remaining instructions from qbrt/logic.h

they're all now in instruction/logic.h
no longer required to implement Stmt::pretty()

this doesn't seem so necessary
compilation for CALL1 and CALL2 instructions

no execution on these yet, but they take the call params directly from registers
stop returning size from print instruction funcs

size is derived from the opcode. no need to return it.