RFC: Fixing comctl32 toolbar tests for different system font heights

[Austin Lund]

I'm trying to fix these test failures:

http://test.winehq.org/data/d4f64121e83671ac10ed6ead04f1c19eb5586cb0/xp_wtb-...

These failures occur because the system font metrics are different to
what is assumed for the hard-coded numbers.

Attached is my go at fixing these (in a three part patch set).  Is
this approach even close to being the right way to do this?