[TYPO3-core] FYI48: #8875: typo3 logo in backend on top left looks not perfect because it has white background on gradient background

[Steffen Kamper]

The following will be committed if noone objects

Type: Cleanup/Feature

Bugtracker references:
http://bugs.typo3.org/view.php?id=8875

Branch: Trunk

When skinning and use other background on topbar in BE the logo needs to 
be transparent.
Attached image is transprent, thx to Cyrill Helg for providing the image

vg Steffen