substantial modifications to genlegit.py

punchangle is taken into account.  Instead of +lookdown and cl_pitchspeed, we
make use of cl_pitchup and cl_pitchdown to set pitch angle.  Also, if +jump and
sv_contjump 0, then +jump is inserted in the generated script until the jump
key is released, in the same way as +duck.  Also, ladder movement is handled
correctly now.