version 52 class files

[Jonathan Gibbons]

JDK 8 folk,

javac currently accepts -target 8, but for convenience has still been 
generating v51 class files.

With new features "coming soon", like lambda and type-annotations, we 
need to update javac to generate v52 class files.

Is there any reason why we should /not proceed to do so -- i..e what 
might fall over if we and when we change javac to use v52 class files, 
and hence have JDK 8 builds contain v52 class files?

-- Jon