QMacStyle: Improvements to some buttons on Yosemite

Radio button, checkbox and non-editable combobox, in normal,
small and mini sizes, and only in the inactive state.

This commit amends 982b9b7ec2441103b100.

Task-number: QTBUG-40833
Change-Id: If3f2bb215e9b8966cbf15f08fa252feb92483c7b
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>