Support appending -i/filename in append_grp2cmd().
Support appending -i/filename in append_grp2cmd().

Store references to in/out filename as INx/OUTy in group type field
(GiTYP). When 3rd parameter to append_grp2cmd() procedure equals
"full", the procedure appends corresponding filename argument/arguments
to cmdline.

Bugfix: use 3 backslashes before $G${1}A$aj in append_grp2cmd() to
prevent premature expansion of GiAj by eval. Similarly, use \\\ before
$$agrptyp.

xrgtn/recode-vid,xrgtn/recode-vid