Merge rdpq to trunk

[snacchus]

This PR merges the following from unstable:

• The rdpq subsystem (excluding font, paragraph and text)
• Required changes to rsp and rspq subsystems for RDP interoperability
• Extensions to sprite.h and surface.h
• Unit tests related to rdpq and RDP-interoperability features of rspq
• Deprecation of the old RDP library
• An example showcasing rdpq: rdpqdemo

Resolves #1 Resolves #54 Resolves #162