build: Allow building with OpenJDK

My local builds with OpenJDK have been successful - no
reason to disallow it, let's go free...

Also allow OpenJDK 7

Conflicts:
	core/main.mk

Change-Id: I01e6cb87e8a7f39db7d762405889221ce287f1ef
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
Allow building with javac 1.7

Change-Id: Id8d78558736482e10c52f2cc86a2b903b1fbdbe5
Don't force building recovery - fixing a 4.4.3 merge derp

Some devices don't have a recovery.img - for example, Xperia Z etc.
This patch comments this out, as it was before the automerge

Change-Id: Ib9c123437cd616551818d3d70d3ff5957ae207fe
Some changes added to compile and run with Java 6 and Java 7.

  - correction of errors with Javac 6:
    - target 1.5 and source empty.
  - correction of errors with Javadoc 7:
    - strange behavior when duplicate classes are given.

Change-Id: Ib814ede143f7799ef18e0fb1b733547519b8b0e5
Merge "build: Allow building with OpenJDK" into kk4.4
Merge "Allow building with javac 1.7" into kk4.4
Merge "Some changes added to compile and run with Java 6 and Java 7." into kk4.4
Merge remote-tracking branch 'slim/kk4.4' into kk44s