add 'extern "C"' to headers

[spraff]

Your policy at the moment is to require applications to add 'extern "C"' to their C++ source files: ​http://trac.ffmpeg.org/wiki/Including%20FFmpeg%20headers%20in%20a%20C%2B%2B%20application

This is silly and annoying.

It is the header file's job to present its interface consistently to applications. decklink_enc.h does this, the other headers should too.

[Clément Bœsch]

We have about 85 C public headers currently. Am I correct to assume that you are asking us to add a C++ boilerplate cruft for every one of them?

Note that in addition to clutter the public header read by our downstreams, it will suggest that FFmpeg headers are C++ compatible, which is NOT the case because it uses C99 specific features in various places, which are not supported by the C++ language.

[Carl Eugen Hoyos]

The headers are C headers and I believe this documented. If you want to use the library with another compiler language, it is your responsibility to ensure the necessary steps are taken.