hush: rework signal and trap handling. Some smaller bits are TODO,

hush: rework signal and trap handling. Some smaller bits are TODO,
 expect minor breakage

function                                             old     new   delta
set_fatal_sighandler                                  12     186    +174
check_and_run_traps                                    -     122    +122
maybe_set_sighandler                                   -      76     +76
hush_main                                            831     887     +56
sigtimedwait                                           -      50     +50
__GI_sigtimedwait                                      -      50     +50
hush_exit                                             49      93     +44
set_mode                                             749     777     +28
pseudo_exec_argv                                     131     151     +20
static.zero_ts                                         -       8      +8
expand_variables                                    1962    1970      +8
builtin_wait                                         172     174      +2
set_misc_sighandler                                   12       -     -12
set_jobctrl_sighandler                                12       -     -12
handler_ctrl_c                                        16       -     -16
builtin_set_mode                                      28       -     -28
handle_trap                                           97       -     -97
handler_ctrl_z                                       107       -    -107
builtin_trap                                         545     438    -107
run_list                                            2149    2006    -143
------------------------------------------------------------------------------
(add/remove: 5/6 grow/shrink: 7/2 up/down: 638/-522)          Total: 116 bytes