control codes in a cc stream can be repeated, and must be ignored.
however, repeated characters must not be ignored. the code attempted to
wipe prev_cmd in handle_char to allow repeated characters to be
processed, but prev_cmd would previously get reset _after_ handle_char()

i also moved the prev_cmd reset out from handle_char() so it can be
re-used for special character sets, which _must_ be ignored when
repeated.