distclean: more closely follow automake's guidelines

According to the documentation, `distclean` should delete files that
`configure` built. Since many of the files we have been declaring for
`distclean-local` are generated by `autoreconf`, avoid deleting several
of those files.

Also, note that the `autom4te.cache` directory is deleted by
`maintainer-clean` already. Most of the others are required for a clean
`configure` run.

To restore the tree to a pristine state, use `git clean -xffd`.

Signed-off-by: Patrick McCarty <patrick.mccarty@intel.com>

Author: phmccarty

Makefile.am

@@ -98,7 +98,10 @@ libbsdiff_la_LDFLAGS = \
 	-Wl,--version-script=$(top_srcdir)/src/bsdiff.sym
 
 distclean-local:
-	rm -rf aclocal.m4 ar-lib autom4te.cache config.guess config.h.in config.h.in~ config.sub configure depcomp install-sh ltmain.sh m4 Makefile.in missing compile
+	-rm -f config.guess~
+	-rm -f config.h.in~
+	-rm -f config.sub~
+	-rm -f configure~
 
 install-exec-hook:
 	perl $(top_srcdir)/findstatic.pl $(top_builddir)/src/*.o | grep -v Checking || :