...where in C++ memchr does not have exactly the two overloads

  void const * memchr(void const *, int, size_t)
  void * memchr(void *, int, size_t)

but rather the C

  void * memchr(void const *, int, size_t)

shining through (see bugreport.apple.com issue 21128245 "non-conforming memchr
in C++"), which gets in the way of the upcoming improved redundant const_cast
check in loplugin:redundantcast.

Change-Id: I7001e74e03429ef23682d52da28fca435130d775