GROOVY-3969: Groovy Console forgets size of input area

Patch supplied by Tai Siew Joon
Fix enum information loss in groovydoc. Fixes #6257

http://jira.codehaus.org/browse/GROOVY-6257
http://groovy.329449.n5.nabble.com/groovydoc-information-loss-for-enums-and-generics-td5716165.html