bpo-39127: Make _Py_HashPointer's argument be const (GH-17690)

Author: petdance

Include/pyhash.h

@@ -8,7 +8,7 @@ extern "C" {
 /* Helpers for hash functions */
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(Py_hash_t) _Py_HashDouble(double);
-PyAPI_FUNC(Py_hash_t) _Py_HashPointer(void*);
+PyAPI_FUNC(Py_hash_t) _Py_HashPointer(const void*);
 PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t);
 #endif
 

Python/pyhash.c

@@ -129,7 +129,7 @@ _Py_HashDouble(double v)
 }
 
 Py_hash_t
-_Py_HashPointer(void *p)
+_Py_HashPointer(const void *p)
 {
     Py_hash_t x;
     size_t y = (size_t)p;