Version 2.1.0 packaging

Just now I released libhinawa v2.1.0:

https://github.com/alsa-project/libhinawa/releases/tag/2.1.0

In the release, I added some arrangement for error reporting. This forces to change symbol table. Although some public symbols are removed, the change brings no regression to applications since they're not defined in public headers yet, fortunately. It's unusual that the existent applications use them.

Additionally, some new functions are added for signal-based asynchronous API. This introduces some new symbols to the table.

For your convenience, I attach a patch for debian/libhinawa2.symbols.

0001-debian-packaging-for-v2.1.0.patch

Cheers!