hg: build-infra/jdk8: If generated-configure is out of date, regenerate it automatically if autoconf is present. (Why didn't we think of this before???)

[magnus.ihse.bursie at oracle.com]

Changeset: 2b500fad0503
Author:    ihse
Date:      2012-10-11 16:56 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk8/rev/2b500fad0503

If generated-configure is out of date, regenerate it automatically if autoconf is present. (Why didn't we think of this before???)

! common/autoconf/configure