The attached patch adds a new Gnus summary buffer command, that clicks a
link in the article buffer. Technically, it calls `widget-button-press'
on one of the widgets in the article buffer, offering completion if
there's more than one. I'm not sure I've handled all the possible values
of the 'gnus-data text property, but more would be easy to add.

Basically this just lets you follow a link without actually moving point
or the mouse into the article buffer.