'configure' apparently doesn't bump the timestamp on config.h if it

didn't have to change it. Useful if you're constantly re-running
configure and want not to have to keep remaking everything, but when I
run configure _from_ my master makefile, it cuts the other way and I
want to avoid having the Makefile rerun configure every time. So
manually touch config.h after a successful run of configure.

git-svn-id: svn://svn.tartarus.org/sgt/agedu@9134 cda61777-01e9-0310-a592-d414129be87e