more memleaks fixed; some cleanup

libraries/librewrite/config.c

libraries/librewrite/context.c

libraries/librewrite/info.c

libraries/librewrite/map.c

libraries/librewrite/params.c

libraries/librewrite/rewrite.c

libraries/librewrite/rule.c

libraries/librewrite/subst.c

libraries/librewrite/xmap.c