GROOVY-6081: Improve unit tests execution time

https://jira.codehaus.org/browse/GROOVY-6081
GROOVY-6081: Improve unit tests execution time (Part 2)

https://jira.codehaus.org/browse/GROOVY-6081
GROOVY-6114: Immutable AST transformation may generate invalid bytecode in combination with @CompileStatic
GROOVY-6119: If an explicit map constructor is provided, the type checker doesn't use it