Updates to llpython.opcode_util to better support loop and exception control flow.
* Inlcuded non-argument branching opcodes in the hasjump opcode list.
* Added all the SETUP_* opcodes to the hascbranch list.
* Modified itercode() to not output the EXTENDED_ARG bytecode.
* Cleaned up extendlabels(), and made it use the hasjump opcode list uniformly.