[Haml] Properly support :suppress_eval for attributes.
[Haml] Properly support :suppress_eval for attributes.

haml/haml,amatsuda/haml,dg1dd1ngs/haml,concord-consortium/haml,stanhu/haml,haml/haml,stanhu/haml,tangposmarvin/haml,tangposmarvin/haml,keithpitty/haml,dg1dd1ngs/haml,nazar-pc/haml,uniba/hamldoc_ja,sideci-sample/sideci-sample-haml,haml/haml,keithpitty/haml,macressler/haml,macressler/haml,haml/haml,nazar-pc/haml