[docu] Improve docu of misc-misplaced-const

[AlexanderLanin]

Summary

East const makes the problem more obvious. With west const people were telling me the const is on the wrong side.

Also it's time to use using instead of typedef.

[aaron.ballman]

East const makes the problem more obvious. With west const people were telling me the const is on the wrong side.

I don't see how this makes the problem more obvious and it seems odd to me that we'd mix styles in code and prose. I prefer leaving this as a west const.

I have no opinion about typedef vs using in this spot, but given that the check can be used in C as well as C++, typedef is slightly more portable.

[AlexanderLanin]

@aaron.ballman I was ready to complain, but you are right. It would make absolutely no sense to move the const, it's just where it should be.

clang-tools-extra/docs/clang-tidy/checks/misc-misplaced-const.rst

 .. title:: clang-tidy - misc-misplaced-const
 
 misc-misplaced-const
 ====================
 
 This check diagnoses when a ``const`` qualifier is applied to a ``typedef``/
 ``using`` to a pointer type rather than to the pointee, because such constructs
 are often misleading to developers because the ``const`` applies to the pointer
 rather than the pointee.
 
 For instance, in the following code, the resulting type is ``int *`` ``const``
 rather than ``const int *``:
 
 .. code-block:: c++
 
-  typedef int *int_ptr;
-  void f(const int_ptr ptr) {
+  using int_ptr = int*;
+  void f(int_ptr const ptr) {
     *ptr = 0; // potentially quite unexpectedly the int can be modified here
-    ptr = 0; // does not compile
   }
 
 The check does not diagnose when the underlying ``typedef``/``using`` type is a
 pointer to a ``const`` type or a function pointer type. This is because the
 ``const`` qualifier is less likely to be mistaken because it would be redundant
 (or disallowed) on the underlying pointee type.