ui: Scale down unit frames larger than 72x72 in the Recruit and Recall dialogs

This is necessary to prevent all list items from being enlarged to fit
the larger units. It is a very common occurrence in campaigns featuring
the Ghost line nowadays thanks to the oversized Spectre baseframe.

This needs to be backported to 1.10.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56455 75b3775d-3801-0410-9e12-e2e43121521d