clean up some harmless warnings
fix spelling error in license for extensions
clean up some core / backend code
add ALSA as a library and backend. not tested yet
Revert "add ALSA as a library and backend. not tested yet"

This reverts commit 6434ec29b380338d8a80c790f45161161182e77f.

I should have been doing this in another branch.
Don't cast away warnings

At least, not if we can use the proper type instead.  If a cast were
necessary, a static_cast<> should be used to force a cast.
Merge remote branch 'kosiini/master' into next
Convert readme and basic_ideas to markdown
Fight bit-rot