Modernize build system a bit.

Mostly rewrite the build system bits with the following changes:

 - Convert to a non-recursive Automake setup.
 - Convert to standard Automake variables where practical.
 - Add rules to regenerate treefuncs as required.
 - Avoid BUILT_SOURCES by adding accurate prerequisites.
 - Remove NOINSTGLOB functionality as it seems pointless.
 - Properly hook generated HTML documentation into Automake.
 - Remove test bits for now, will be reintroduced later.
 - Simplify configure.ac.