#2 Fix some const-related warnings

[Mikhail T.]

The patch below provides for warning-less compiles with
Tcl-8.4 (constified) and Tcl-8.3 (not constified). Helps future
hacking greatly by eliminating noise in the warnings.

This patch is part of the FreeBSD port

http://www.freshports.org/devel/tcl-trf/

see also:

http://www.freebsd.org/cgi/cvsweb.cgi/ports/devel/tcl-trf/files/

[Mikhail T.]