shell: unify endofname() in hush and ash

shell: unify endofname() in hush and ash

function                                             old     new   delta
builtin_umask                                        132     133      +1
changepath                                           195     194      -1
expand_and_evaluate_arith                             77      69      -8
ash_arith                                            143     135      -8
expand_one_var                                      1551    1515     -36
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/4 up/down: 1/-53)             Total: -52 bytes

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>