Improve name lookup for and template instantiation of declaration

Improve name lookup for and template instantiation of declaration
references. There are several smallish fixes here:

  - Make sure we look through template parameter scope when
    determining whether we're parsing a nested class (or nested class
    *template*). This makes sure that we delay parsing the bodies of
    inline member functions until after we're out of the outermost
    class (template) scope.
  - Since the bodies of member functions are always parsed
    "out-of-line", even when they were declared in-line, teach
    unqualified name lookup to look into the (semantic) parents.
  - Use the new InstantiateDeclRef to handle the instantiation of a
    reference to a declaration (in DeclRefExpr), which drastically
    simplifies template instantiation for DeclRefExprs.
  - When we're instantiating a ParmVarDecl, it must be in the current
    instantiation scope, so only look there.

Also, remove the #if 0's and FIXME's from the dynarray example, which
now compiles and executes thanks to Anders and Eli.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72481 91177308-0d34-0410-b5e6-96231b3b80d8