Notes and image:
http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.66/Usability
- now each editor has own settings for "show panel header" and
"show panel background", and colors+alpha for this.
- this setting used to be global for all editors, but it can conflict
with looks of specific editors.
- Now you can set for editors to show panels with a 100% transparent
tool/properties region.
Note: read XML theme files now might get an error, Campbell will fix.