Makefile: remove tracking of TCLTK_PATH

Makefile: remove tracking of TCLTK_PATH

It looks like we are tracking the value of TCLTK_PATH in the main
Makefile for no good reason.

This patch removes the useless code used to do this tracking.

Maybe this code should have been moved to gitk-git/Makefile by
62ba514 (Move gitk to its own subdirectory, 2007-11-17).
A patch to do that has just been sent to Paul Mackerras, the gitk
maintainer.

While at it, this patch removes /gitk-git/gitk-wish from
.gitignore as it should be in /gitk-git/.gitignore and the patch
sent to Paul put it there.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>