media stream types

[ichthyo]

design a framework for dealing with different kinds of media, thereby avoiding hard wired code paths as in cinelerra. Especially, the purpose is to create a somewhat generic implementation of the wiring within the builder.

At least initially this mainly boils down to defining a scheme how to map the type definitions used by individual media handling libraries, and especially by GAVL.

[ichthyo]

A first draft/plan for this framework is  here; more details to be worked out when actually integrating GAVL and other plugin/media handling libraries

[ichthyo]

introduced a typedef for StreamType::ID to denote an entryID<Streamtype>. Basically this gets us an immutably mixed symbolic/hash ID, with several automatic conversions; later on, entryID is expected to be automatically registered in some type translation tables, which then would automatically asure unique and distinct stream type definitions.