v0.5.6 Closure.withDelegate doesn't work outside of the tests.

[timyates]

So, the tests pass, the groovydoc testcase of

 * <pre class="groovyTestCase">
 *   def testClosure = { num ->
 *       num + val
 *   }
 *
 *   def value = testClosure.withDelegate( [ val: 4 ] )( 3 )
 *   assert value == 7
 * </pre>
 *

passes, but if you @Grab the library, Groovy claims to have no knowledge of withDelegate 🐼

Needs investigation and possible bug reports