Revert "[c++1z] P0195R2: Support pack-expansion of using-declarations."

This reverts commit r290080 as it leads to many Clang crashes, e.g.:
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-quick/builds/1814

llvm-svn: 290092
diff --git a/clang/test/Parser/cxx1z-using-declaration.cpp b/clang/test/Parser/cxx1z-using-declaration.cpp
index 0be8167..dab1ca8 100644
--- a/clang/test/Parser/cxx1z-using-declaration.cpp
+++ b/clang/test/Parser/cxx1z-using-declaration.cpp
@@ -10,10 +10,10 @@
 }
 
 struct X {
-  int x1, x2, y, z; // expected-note 2{{conflicting}}
+  int x1, x2, y, z; // expected-note {{conflicting}}
 };
 struct Y {
-  int x1, x2, y, z; // expected-note 2{{target}}
+  int x1, x2, y, z; // expected-note {{target}}
 };
 struct Z : X, Y {
   using X::x1,
@@ -28,8 +28,3 @@
 int X::*px2 = &Z::x2;
 int Y::*py = &Z::y;
 int X::*pz = &Z::z;
-
-template<typename ...T> struct Q : T... {
-  using T::z...; // expected-error {{conflicts}}
-};
-Q<X,Y> q; // expected-note {{instantiation of}}