Debugging a panel plugin with valgrind

[Nick Schermer]

Jasper and I moved them out of the panel because we both don't
maintain them there (the readme file) and it's not easy to find. The
(internal) sample plugin was also not 'maintained'.

Therefore I've moved the docs into the wiki and started writing the
xfce4-sample-plugin. The sample plugin will be external, with a the
needed info to create an internal plugin.

Personally I vote for keeping all the how to's on 1 place and not
spreading them all over the projects/websites. This way people can
also help improving the tutorial. So keep the goodies.xfce.org domain
for the goodie websites and put all faqs/howtos and stuff on
wiki.xfce.org.

Happy Xmas && 2K7,
Nick