hexdump: code shrink

hexdump: code shrink

function                                             old     new   delta
remap                                                173     178      +5
move_mapping_lower                                   107     109      +2
move_mapping_further                                 141     143      +2
hexedit_main                                        1191    1176     -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/1 up/down: 9/-15)              Total: -6 bytes

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