hg: build-infra/jdk8: Added mention of sjavac and FILTER tricks that was added to the guide.

[kelly.ohair at oracle.com]

Changeset: f2c6b4996213
Author:    ohair
Date:      2013-02-23 11:02 -0800
URL:       http://hg.openjdk.java.net/build-infra/jdk8/rev/f2c6b4996213

Added mention of sjavac and FILTER tricks that was added to the guide.

! README-builds.html