Fixing mcedit transparent problem in mc 4.7.0.x series

In previous release of mc, we just need to add following code to make it transparent in [Colors] section:

base_color=normal=editnormal=,default:

But since version 4.7.0.x (using in Ubuntu 10.04 and later) it doesn't work. Especially while using mcedit, it looks ugly. it still using normal background color for empty space, see this bug.

To make it works again, replace code above with this: