libauto: more obscene hackery to make it work on LLVM 4

This sort of thing is going to get revamped to be less hackish soon but
for now I want it to work. In this particular case, libc++ 4 (and maybe
earlier) gets very upset if we're imprecise about our const markers, and
I guess libauto was careless. This fixes it (PtrPtrMap) to be correct.

pkgs/os-specific/darwin/apple-source-releases/libauto/default.nix

···
       --replace "#include <msgtracer_client.h>" ''$'#include <asl.h>\nstatic void msgtracer_log_with_keys(...) { };'
 
     substituteInPlace Definitions.h \
-      --replace "#include <System/pthread_machdep.h>" ""
+      --replace "#include <System/pthread_machdep.h>" "" \
+      --replace 'void * const, void * const' 'void * const, void *'
 
     # getspecific_direct is more efficient, but this should be equivalent...
     substituteInPlace Zone.h \