Creation and export of header-only Thrift-generated libraries about yarp

[paulfitz]

I've now modified the translation of thrift structures to put function bodies in cpp files rather than leaving them lazily in header files (0c7645b). Enums and services appear to already generate cpp code. Are there any remaining elements that need work?

[elen4]

That should be all, unless somebody creates thrift files that contain only typedefs and constants 😕

[paulfitz]

It should be less surprising to a user that such a file wouldn't generate code. Maybe a macro for exporting should add a dummy cpp to guarantee there is source? I'm not sure yarpidl_thrift is the best place to enforce that, although if it is inconvenient to do elsewhere I'm not against it.