[PATCH] gitk: make Ctrl "+" really increase the font size

[PATCH] gitk: make Ctrl "+" really increase the font size

Only Ctrl "=" was bound to increase the font size, probably because
English keyboards have the plus on the same key as the equal sign.
However, not the whole world is English, and at least with some
other keyboard layouts, Ctrl "+" did not work as documented.

Noticed by Stephan Hennig.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>