This also removes some cruft, and makes handling of {CXX,LD}FLAGS more
consistent.

This is a significant refactoring of the statistical inference code,
with many cleanups and improvements, and is aimed towards future
extensibility.

The old community module is available as 'community_old' and will be
completely removed in the near future.

This also makes autogen.sh compatible with older versions of autotools +
pkg-config.