c++: Deducing type from initializer_list<auto> [PR93107]

c++: Deducing type from initializer_list<auto> [PR93107]

In this testcase we weren't able to deduce b's type:

  template<typename T> void Task() { }
  auto b = { &Task<int> };

because resolve_nondeduced_context doesn't iterate on the {}'s elements.
So make sure to look into {} too.  We don't need to handle nested {}
here.

We could either tweak resolve_nondeduced_context to handle CONSTRUCTORs
or add a _ctor version, but then resolve_nondeduced_context_or_error
would need some changes too -- it'd have to check the result of a call
to r_n_c for each element.

gcc/cp/ChangeLog:

	PR c++/93107
	* pt.c (do_auto_deduction): Call resolve_nondeduced_context for
	the elements of a { } list.

gcc/testsuite/ChangeLog:

	PR c++/93107
	* g++.dg/cpp0x/initlist-deduce3.C: New test.