hush: get rid of charmap[]

hush: get rid of charmap[]

function                                             old     new   delta
parse_stream                                        1447    1508     +61
get_local_var_value                                    -      31     +31
run_list                                            2018    2020      +2
pseudo_exec_argv                                     151     149      -2
maybe_set_sighandler                                  50      47      -3
hush_exit                                             93      90      -3
builtin_wait                                         275     272      -3
check_and_run_traps                                  169     164      -5
hush_main                                            985     977      -8
file_get                                             260     240     -20
builtin_trap                                         438     414     -24
set_in_charmap                                        30       -     -30
lookup_param                                          31       -     -31
parse_and_run_stream                                 153      54     -99
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 2/9 up/down: 94/-228)          Total: -134 bytes