xdu: fix homepage/url breakage

Comments in the formula explain. Homepage/URL have been dead for, well,
years apparently. We could probably boneyard it, but since Debian and
Ubuntu have working links, keeping it around isn’t too odious.

Closes #7.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
pgplot 5.2.2: Add mirror
pgplot: update 5.2.2_1 bottle.