build: Fix autotools warning

I don't really know what AM_PROG_CC_C_O actually does, but
autotools seems to want it
build: Use proper libtool library versioning

At least, I think this is the proper way to do it.
build: Bump version to match Gnome version
build: Use xz for dist tarballs
Revert "build: Bump version to match Gnome version"

Actually, let's not do this. GSound is a small library and
(bugfixes apart) isn't likely to be updated frequently,
especially as libcanberra isn't changing much.

This reverts commit 45c1404a94ee0fe214e94f53f33952ad8dd46201.
build: Use a more sensible first release number

This is version 1.0.0
docs: Update canonical documentation location