Update RELEASENOTES.md

Update configure.ac

Combines 2.8.4.6 and 2.8.4.5
Add a new `alsa` configuration setting: `use_mmap_if_available` to control the use of mmap. 
Handle varying packet lengths -- this makes it compatible with the HTC Connect, HTCs AirPlay implementation.

Update configure.ac

Update RELEASENOTES.md

Create INSTALL.md

Update RELEASENOTES.md

Update README.md

Update RELEASENOTES.md

Update RELEASENOTES.md

Update configure.ac