Revert "[libc++] Fix PR35491 - std::array of zero-size doesn't work with non-default constructible types."

Revert "Fix initialization of array<const T, 0> with GCC."
Revert "Make array<const T, 0> non-CopyAssignable and make swap and fill ill-formed."

This reverts commit r324182, r324185, and r324194 which were causing issues with zero-length std::arrays.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@324309 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/containers/sequences/array/begin.pass.cpp

@@ -31,13 +31,4 @@ int main()
         *i = 5.5;
         assert(c[0] == 5.5);
     }
-    {
-      struct NoDefault {
-        NoDefault(int) {}
-      };
-      typedef NoDefault T;
-      typedef std::array<T, 0> C;
-      C c = {};
-      assert(c.begin() == c.end());
-    }
 }