[libwspcodec] 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
Merge pull request #5 from monich/wsp_text_header_iter_gone

Took out wsp_text_header_iter stuff