allow new T only if T is constrained to having a constructor

git-svn-id: http://haxe.googlecode.com/svn/trunk@6226 f16182fa-f095-11de-8f43-4547254af6c6
raise and catch a proper error while expr mapping generics (fixed issue #1508)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6227 f16182fa-f095-11de-8f43-4547254af6c6
=> is right associative

git-svn-id: http://haxe.googlecode.com/svn/trunk@6228 f16182fa-f095-11de-8f43-4547254af6c6
unit test fix

git-svn-id: http://haxe.googlecode.com/svn/trunk@6229 f16182fa-f095-11de-8f43-4547254af6c6