Fix 'make distcheck'.

The 'make distcheck' rule is showing up two errors.  The lib/
directory (and contents) are not being included in the distribution, and
the results/ directory (created by running make check) is not being
cleaned up as part of a make distclean.  All fixed in this commit.

ChangeLog:

	* Makefile.am (EXTRA_DIST): Add lib directory.
	(distclean-local): New rule, cleanup results directory.
	* Makefile.in: Regenerate.