package/gtkmm3: use correct versions of mm packages

Many of the C++ wrapper packages had API changes. These changes where
never introduced in gtkmm3, meaning that older, but still maintained
versions are needed to build gtkmm3.

Fixes:
 - http://autobuild.buildroot.net/results/172/17263ac51f197031106eb7fd595126a2720f0397



Signed-off-by: Daniel Lang <d.lang@abatec.at>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>