Use node_access to check create permission

Right now, the code checks if the user as the right to create a new node of a given type using user_access("create $type content"); . While that's the standard permission name for node type created by node.module, it's not always the case. I would suggest moving to node_access('create', $type) which is designed exactly for the purpose of checking if the user has the right to create a node of a given type.

Attached patch does that.