Rename config/ as build-aux/ to match with up-to-date coding
	standards.
	
	* config/Makefile.am, config/bison++.in,
	* config/move-if-change, config/readline.m4:
	Move to...
	* build-aux/Makefile.am, build-aux/bison++.in,
	* build-aux/move-if-change, build-aux/readline.m4:
	... here.
	* configure.ac, Makefile.am, src/parse/Makefile.am:
	Adjust accordingly.