phasesplit v1.0.0

Stereo centre/side separation and channel processing.

The centre and the sides always add back up to the input, so nothing
is invented and nothing is lost, and content panned hard to one side
gives a centre of exactly zero.

Each archive holds a single binary with no dependencies beyond the
system libraries. Unpack it anywhere and run it. To check the build
on your own machine:

phasesplit --selftest

Built and tested on Linux, macOS and Windows by the workflow that
produced this release.