Test:

* "composite" alpha blending modes

* BShape conversion and rendering

* Bezier curve rendering



Implement:

* "escapment_delta" text rendering

* font shearing

* handling of other BBitmap colorspaces



Improve:

* make special case versions of some functions:

- horizontal/vertical lines
- horizonzal text rendering, using scanline cache

* make special verions of DrawingModes for B_SOLID_* patterns

* get rid of virtual function use in DrawingMode framework

