c++: member alias declaration [PR103968]

Here, we were wrongly thinking that (const Options&)Widget<T>::c_options is
not value-dependent because neither the type nor the (value of) c_options
are dependent, but since we're binding it to a reference we also need to
consider that it has a value-dependent address.

	PR c++/103968

gcc/cp/ChangeLog:

	* pt.cc (value_dependent_expression_p): Check
	has_value_dependent_address for conversion to reference.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/alias-decl-mem1.C: New test.