[string.view.template.general] Use const charT* for data

and a data member, for the consistency with `basic_string`.

Author: frederick-vs-ja

source/strings.tex

@@ -665,7 +665,7 @@
     constexpr const_reference at(size_type pos) const;                  // freestanding-deleted
     constexpr const_reference front() const;
     constexpr const_reference back() const;
-    constexpr const_pointer data() const noexcept;
+    constexpr const charT* data() const noexcept;
 
     // \ref{string.view.modifiers}, modifiers
     constexpr void remove_prefix(size_type n);
@@ -734,7 +734,7 @@
     constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
 
   private:
-    const_pointer @\exposid{data_}@;        // \expos
+    const charT* @\exposid{data_}@;         // \expos
     size_type @\exposid{size_}@;            // \expos
   };