Now that we have declared/defined tag types within DeclGroups,

Now that we have declared/defined tag types within DeclGroups,
instantiation of tags local to member functions of class templates
(and, eventually, function templates) works when the tag is defined as
part of the decl-specifier-seq, e.g.,

  struct S { T x, y; } s1;

Also, make sure that we don't try to default-initialize a dependent
type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72568 91177308-0d34-0410-b5e6-96231b3b80d8