Remove dependency on libstdc++

[newhoggy]

This fails to build in the absence of libstdc++. Looking at the source code it doesn't look like the c-bits actually use any C++ functionality.

[chadaustin]

I'd support this change. I don't have time to implement it immediately but if you want to put together a PR I could get it landed and released.

[chadaustin]

This dependency was added as part of #12

@robdockins Can you clarify what systems needed this change?

I tried to convert the .cpp files to .c last night but I couldn't figure out how to convince Cabal to build them in C mode rather than C++ mode. If I could reproduce @robdockins's original issue, it probably wouldn't be hard to break the dependency on libstdc++.

[robdockins]

Sorry, I've paged out the original context for that request... I think it may have been Windows builds that were causing me trouble at the time, but I don't recall for sure.

[chadaustin]

0.2.4.7 is released with all of the FFI bits replaced with C99 instead of C++ code.

[newhoggy]

Thanks!