ConcurrentHashMap/ConcurrentMap/Map.compute

[Doug Lea]

A fixed-up successfully jdk8-javadoc'ed version of Map is now at
  http://gee.cs.oswego.edu/dl/wwwtmp/apis/Map.java
with displayable javadoc at:
  http://gee.cs.oswego.edu/dl/wwwtmp/apis/java/util/Map.html

Comments? Complaints? If not, feel free to integrate.

(Arne: thanks for pointing out that "merge" was mangled.)

Side note about this and a few other upcoming cases:
We must keep j.u.c sources independent, so normally commit
to jsr166 and then integrate into openjdk. But ad-hoc
mechanics seem the only way to deal with updates to
existing files. Handing off is likely nicer than directly
committing into lambda.

-Doug