[Done for V0.38] Interface graphics flexibility

[beowuuf]

Based on conversation in the bugs forum about changing the interface graphics:

1) Could the full 640x480 image be used, making it possible to do some quite nifty organic style interfaces

2) Can the semi-transparent boxes that are used to dim out parts of the interface (when sleeping for example) use bitmaps, so they can be changed (so not fixed sizes/positions)

[Gambit37]

I believe (1) is now fully fixed (there were some issues with the text area and stuff -- need to double check.

(2) would be lovely -- without this, all interfaces will have the same boxes in the same place and will still look like DM.

[George Gilbert]

(2) now works too...(the position of the masking is taken from the position of the underlying interface bitmap - move that and the mask will work correctly automatically).