Changes in internal API:
* Every route attribute must be defined as struct ea_class somewhere.
* Registration of route attributes known at startup must be done by
ea_register_init() from protocol build functions.
* Every attribute has now its symbol registered in a global symbol table
defined as SYM_ATTRIBUTE
* All attribute ID's are dynamically allocated.
* Attribute value custom formatting hook is defined in the ea_class.
* Attribute names are the same for display and filters, always prefixed
by protocol name.
Also added some unit testing code for filters with route attributes.
- Unit Testing Framework (BirdTest)
- Integration of BirdTest into the BIRD build system
- Tests for several BIRD modules
Based on squashed Pavel Tvrdik's int-test branch, updated for
current int-new branch.
