hush: fix multimple dependent variable expansion cases

hush: fix multimple dependent variable expansion cases

function                                             old     new   delta
get_local_var_value                                  100     171     +71
expand_assignments                                    46      76     +30
reset_traps_to_defaults                              229     238      +9
maybe_set_to_sigexit                                  47      50      +3
init_sigmasks                                        211     214      +3
builtin_trap                                         462     465      +3
expand_vars_to_list                                 2412    2408      -4
run_pipe                                            1568    1533     -35
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 6/2 up/down: 119/-39)            Total: 80 bytes

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