Fix make clean and make install.

Fix make clean and make install.

Commit 77aa6680 replaced the hardcoded list of binaries in Makefile.in
by the autoconf macro @executables@. However, the "install" and the
"clean" targets still used the now undefined $(BINARIES) variable. This
caused "make clean" to not remove any executables and "make install"
to fail with

	/usr/bin/install -c -s -m 755  /usr/local/bin
	/usr/bin/install: missing destination file operand after `/usr/local/bin'
	Try `/usr/bin/install --help' for more information.

Fix this bug by using @executables@ rather than $(BINARIES).