*: use better isspace implementation

*: use better isspace implementation

function                                             old     new   delta
asciifile                                             90     106     +16
expand                                               653     658      +5
skip_non_whitespace                                   21      25      +4
bb_iswspace                                           25      28      +3
readcmd                                             1071    1072      +1
find_range                                           496     497      +1
singlemount                                          772     771      -1
ifupdown_main                                       2134    2133      -1
edir                                                 370     369      -1
volume_id_set_label_string                            82      79      -3
trim                                                  85      82      -3
rtc_adjtime_is_utc                                   141     138      -3
rewrite                                             1039    1036      -3
do_cmd                                              4465    4462      -3
bb_dump_add                                          358     355      -3
awk_split                                            553     550      -3
fbset_main                                          1273    1268      -5
skip_thing                                           259     253      -6
get_trimmed_slice                                     46      39      -7
bb__parsegrent                                       245     238      -7
parse_file_cmd                                       116     108      -8
check                                               1532    1523      -9
bb__pgsreader                                        198     188     -10
dot_skip_over_ws                                      61      46     -15
colon                                               3032    3012     -20
if_readlist_proc                                     655     634     -21
normalize                                            193     165     -28
add_cmd                                             1162    1133     -29
get_key                                              528     476     -52
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 6/23 up/down: 30/-241)         Total: -211 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>