Latest push for command substitutions

[Chet Ramey]

The latest devel branch push has a rewrite of parse_comsub() to recursively
call the parser (yyparse()). I was finally able to get all the state
working correctly, though it will probably only work with bison.

Please run it through any tests or scripts you have so we can shake out any
bugs early.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/