improved error messages of invalid redefinitions

git-svn-id: http://haxe.googlecode.com/svn/trunk@5961 f16182fa-f095-11de-8f43-4547254af6c6
added levenshtein spell check (fixed issue #1425)

git-svn-id: http://haxe.googlecode.com/svn/trunk@5962 f16182fa-f095-11de-8f43-4547254af6c6
do not allow recursive abstract subtypes

git-svn-id: http://haxe.googlecode.com/svn/trunk@5963 f16182fa-f095-11de-8f43-4547254af6c6