ash: minor shrink (mostly smallints) and variable renaming

ash: minor shrink (mostly smallints) and variable renaming

function                                             old     new   delta
optschanged                                           85      91      +6
tryexec                                              115     118      +3
xxreadtoken                                          290     292      +2
raise_error_unexpected_syntax                         75      77      +2
bltincmd                                               6       8      +2
parseheredoc                                         128     129      +1
static.is_interactive                                  4       1      -3
readtoken                                            156     153      -3
lasttoken                                              4       1      -3
evalcommand                                         1147    1144      -3
checkkwd                                               4       1      -3
back_exitstatus                                        4       1      -3
pipeline                                             282     276      -6
list                                                 369     360      -9
ash_main                                            1402    1393      -9
options                                              616     606     -10
readtoken1                                          2823    2811     -12
parse_command                                       1529    1507     -22
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 6/12 up/down: 21/-91)           Total: -70 bytes
   text    data     bss     dec     hex filename
 807603     611    6908  815122   c7012 busybox_old
 807545     611    6900  815056   c6fd0 busybox_unstripped