* src/dfa.c (dfastate): Add argument UC, the current input character.
Fill only a group including the character in transition table.
(realloc_trans_if_necessary): Add the dummy state which means that a
transition table is assigned but the next state is not assigned.
(build_state): Return the next state. All callers updated.
(transit_state_singlebyte): If we get the dummy state,
fill the transition table.
(dfaexec_main): Handle the dummy state.
(free_mbdata, dfafree): Consider the dummy state.