The parser will now always generate Identifier nodes (for
non-namespaced identifiers). This obsoletes the useIdentifierNodes
parser option.
Node constructors still accepts strings and will implicitly create
an Identifier wrapper. Identifier implement __toString(), so that
outside of strict-mode many things continue to work without changes.
The new dereferencing syntaxes (new Foo)->bar and (new Foo)['bar'] were
causing a shift/reduce conflict with the '(' expr ')' rule. When
(new Foo) was encountered (without dereference operators following) the
parser thus threw a parse error.
The fix simply adds a special '(' new_expr ')' rule to expr. This does not
remove the shift/reduce conflict itself, but makes it irrelevant.
This fixes issue #20.
