Incorrect end position in a lot of nodes

[duaraghav8]

A lot of definitions in the grammar are similar to

id:Identifier __ params:("(" __ InformalParameterList? __ ")")?

Notice that the first whitespace directive __ should exist inside params rather than before it. here, it exists before it. This means in a code construct like

contract Foo is bar, baz                         {
}

the end position of the Modifier baz actually covers al the whitespace after baz instead of just covering till z. This is a problem with lot of node definitions where everything after the whitespace __ is optional.