ls: make color-related code more readable. Fix a case when

ls: make color-related code more readable. Fix a case when
 it was working non-deterministically.

function                                             old     new   delta
bold                                                   -      34     +34
showfiles                                           1508    1495     -13
fgcolor                                               50      34     -16
bgcolor                                               34       -     -34
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 0/2 up/down: 34/-63)            Total: -29 bytes