Now that dialog4ports was committed, which brings support for mixed checkbox
and combobox dialogs, with great pleasure backout r305288 by dougb@ (which
had dropped the word 'support' from most places that it occured) and restore
original readability of those descriptions. This also improves consistency.
While here, move GIO description to standard pool, as advised by comment.
Tested with: www/firefox (on RELENG_8)