msh: shrink, mainly by using smallints

msh: shrink, mainly by using smallints

function                                             old     new   delta
synio                                                251     263     +12
filechar                                             310     315      +5
subgetc                                              781     785      +4
brkcontin                                            106     109      +3
...
yylex                                                981     976      -5
execute                                             2513    2508      -5
waitfor                                              321     315      -6
onintr                                               103      97      -6
doset                                                332     326      -6
doexec                                               186     180      -6
yyparse                                               65      57      -8
thenpart                                             135     126      -9
forkexec                                            1379    1370      -9
onecommand                                           457     433     -24
newtp                                                 52      28     -24
command                                             1086    1061     -25
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 7/23 up/down: 27/-163)         Total: -136 bytes