Took out wsp_text_header_iter stuff

Those functions were parsing a strange representation of textual Content-Type like headers but the syntax they understood wasn't HTTP compliant. This is pretty useless, has nothing to do with WSP and doesn't belong here.

Also changed versioning a bit. Now application would be linking against libwspcodec-X.Y.so rather than libwspcodec.so.X

Tag it as 2.1