Add operator overloading section to Groovy specification.
GROOVY-5957: groovydoc does not create links for non-fully qualified classes in same package
tweak typing doco wording
Merge pull request #455 from paulk-asert/groovy5957

GROOVY-5957: groovydoc does not create links for non-fully qualified cla...
Merge pull request #454 from pledbrook/doc-patch-02

Add operator overloading section to Groovy specification.
Documentation of simple rules for type checking assignments