Bind non-keypad +/-/* to font adjustments: Bug #731244
Compile with Vala 0.24: Bug #737227

Bad GTK+ 3.12 binding in 0.24 is corrected in 0.26, so adding that
binding to our project.  Will want to remove when 0.26 becomes req'd
minimum for California.
Merge branch 'master' into wip/729029-stutter