Switch the required host Java environment to 1.6.

The path to the Java toolchain is now explicitly
specified so no manual configuration should be
required.

Change-Id: I84abc122c557372e77e4579e9a9efe56af2b412c

The java version changed, and we made envsetup automatically find the right JAVA_HOME.

This change forces everyone to re-source envsetup.sh

Change-Id: Ieb9512d5725cca26a83debf9b0480bc20e19d5ee

Fix javadoc for Java 6.

If you don't set bootclasspath, there would be errors like:
javadoc: error - In doclet class DroidDoc, method start has thrown an exception java.lang.reflect.InvocationTargetException

Change-Id: I1b83360cb595d50577c6043d6e91b0f92e4c04d6

Avoid inheriting PRIVATE_BOOTCLASSPATH from moduels that depend on api-stubs-timestamp

The inherited value has caused build breakage on Mac build.

Change-Id: I8a1b1d6c6d411f6aaaee2d8dbd0297e3d60ab5c2

Ignore STAY_OFF_MY_LAWN when setting JAVA_HOME.

Don't check STAY_OFF_MY_LAWN in set_java_home.  That function already
refuses to update JAVA_HOME if it's set to something, which should
be sufficient for anybody who doesn't want the script to mess with it.

With this change, you can get the benefits of the 1.5/1.6 auto-selection
without having to suffer through window title changes.

Change-Id: I5cfc5d6fdf26a10b42b52925f877012c0506b9a5