Remove a pile of old SGML stuff we no longer need in dtdocbook since
we use NSGMLS.
Use some TCL macros from m4/tcl.m4 to loacate and use information in
the tclConfig.sh script installed with TCL. I had to modify it to
export TCL_INCLUDE_SPEC, which was present but not imported.
In this commit, we convert FreeBSD and OpenBSD to use a system version
of TCL (8.6).
We also get rid of the hairy and buggy "CompareI18NStrings" custom Tcl
function and use the newer Tcl's builtin dictionary sort mechanism for
generating the Indexes and Glossaries, which were silently broken in
previous commits.
It was just not possible to use the same Tcl code in modern versions
of Tcl in addition to the ancient version included with CDE - so, now
we will always depend on the system version. It's been tested with
8.6 and 8.7 versions of Tcl with great results.
One issue that came up was attempting to read array values indexed by
a key that didn't exist when generating indexes and glossaries.
I am not sure why this hasn't been a problem before, but for now, we
simply won't try to emit array values for non-existant array indexes.
