* doc/gen-examples-outputs-mk: Take sources as input instead of
	programs.
	* doc/examples-outputs.mk: Regen.
	* doc/Makefile.am ($(DOC_SRCDIR)/examples-outputs.mk):
	Adjust caller.
	Use `find' to get inputs instead of relying on
	$(PROGRAMS_examples).
	Rename target as...
	($(srcdir)/examples-outputs.mk): ...this.
	Depend only on $(srcdir)/gen-examples-outputs-mk, and no longer on
	$(srcdir)/Makefile.am.
	(regen-examples-outputs-mk): Adjust as well.
	* doc/programs-examples.mk: Adjust comments.