crecord: update uiheader docstring There's no need to move anything to patch.py. The uiheader class only has methods relevant to crecord and overrides __getattr__ in order to use `patch.header` objects as a sort of mixin.

crecord: add skipfolded param to previtem This just simplifies the API a bit so it matches `nextitem` and I can handle both nextitem and previtem symmetrically.

dispatch: don't attempt to import debugger as bytestring The __import__ thingie needs a string, not a bytestring. Guess I'm the only one who uses this once in a while and noticed it was broken.