Renames parameterstream_impl to stringstream_proxy and parameterstream to string_stream. - The workaround for gcc < 5 now does not get built at all (since it is unused) for other compilers. - Pulled all stringstream_proxy method implementations into the class declaration to keep it as small as possible.
Renames parameterstream_impl to stringstream_proxy and parameterstream to string_stream.
- The workaround for gcc < 5 now does not get built at all (since it is unused) for other compilers.
- Pulled all stringstream_proxy method implementations into the class declaration to keep it as small as possible.

adishavit/argh,adishavit/argh