tbl bug + fix

[Guy Harris]

>>tbl will dump core if given a long (>256) input line for a text block...
>
>Tbl has numerous problems with excessively long lines or fields.  There
>is no quick, simple fix; a major overhaul is required.

Well, it depends.  "tbl" was changed in some SunOS release, with a non-major
overhaul, not to drop core in at least some of those situations; this
does not completely eliminate the problems, though - it just makes "tbl"
report them somewhat more politely.  (I presume the "major overhaul"
would be to fix it to handle long lines or fields, not just complain
about them.)  If I remember correctly, a number of procedure calls were
changed to take buffer-length arguments, but this was not really a major
overhaul.