autogen.sh script to create configure, et al.

It's become custom to create a script called autogen.sh, which creates
all the auto-generated files using all the appropriate auto* tools when
run, so one doesn't have to worry about checking them into the repository.
This seems like a good idea, follow suit.

autogen.sh

@@ -0,0 +1,7 @@
+#!/bin/sh -xe
+#
+# Simple script to run the appropriate autotools from a repository.
+#
+autoheader
+autoconf
+rm -rf autom4te.cache config.log