ExecutorService's type parameters changed between JDK5 and JDK6 in a
way that makes it impossible for our invokeAll/invokeAny methods to
match both at compile time. This project builds a JDK6-like copy of
ExecutorService (but with JDK5 compiler settings to ensure that it will
work with JRE5 at runtime). It also builds a version of
AbstractExecutorService that is equivalent to a JDK5 version but using
the JDK6 type parameters for the invokeAll/invokeAny methods just as with
ExecutorService. This project's is then used in the bootstrap class path
of Guava proper.