opencv_2.4: Update HOMEPAGE

Old link is dead

ricardo@neopili:~$ wget http://opencv.willowgarage.com/wiki/
--2015-08-19 17:12:44--  http://opencv.willowgarage.com/wiki/


Resolving opencv.willowgarage.com (opencv.willowgarage.com)...
70.35.54.199
Connecting to opencv.willowgarage.com
(opencv.willowgarage.com)|70.35.54.199|:80... failed: Connection timed
out.
Retrying.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>