API: Make header just work with C++
API: Make header just work with C++

It can now be included bare in C++ files, instead of wrapped
in an extern "C" block.

Signed-off-by: Derek Buitenhuis <aff7d637ede26ea82e5226e01b697996cc52e526@gmail.com>

silverfilain/L-SMASH,canbal/l-smash,maki-rxrz/L-SMASH,silverfilain/L-SMASH,l-smash/l-smash,l-smash/l-smash,maki-rxrz/L-SMASH,canbal/l-smash,l-smash/l-smash,silverfilain/L-SMASH