ash,hush: history builtin

function                                             old     new   delta
show_history                                           -      39     +39
builtin_history                                        -      16     +16
historycmd                                             -      13     +13
bltins1                                              312     324     +12
builtintab                                           336     344      +8
popstring                                            134     140      +6
hush_main                                           1048    1046      -2
ash_main                                            1398    1396      -2
size_from_HISTFILESIZE                                44      40      -4
------------------------------------------------------------------------------
(add/remove: 3/0 grow/shrink: 3/3 up/down: 94/-8)              Total: 86 bytes

Signed-off-by: Flemming Madsen <busybox@themadsens.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
vi: make regexp search case-insensitive if ":set ignorecase" is active

Reported by Dan Moinescu <dan@moinescu.net>.

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