bpo-40602: Rename hashtable.h to pycore_hashtable.h (pythonGH-20044)

* Move Modules/hashtable.h to Include/internal/pycore_hashtable.h
* Move Modules/hashtable.c to Python/hashtable.c
* Python is now linked to hashtable.c. _tracemalloc is no longer
  linked to hashtable.c. Previously, marshal.c got hashtable.c via
  _tracemalloc.c which is built as a builtin module.

Author: vstinner

Modules/Setup.dist

@@ -135,7 +135,10 @@ zipimport zipimport.c
 faulthandler faulthandler.c
 
 # debug tool to trace memory blocks allocated by Python
-_tracemalloc _tracemalloc.c hashtable.c
+#
+# bpo-35053: The module must be builtin since _Py_NewReference()
+# can call _PyTraceMalloc_NewReference().
+_tracemalloc _tracemalloc.c
 
 # The rest of the modules listed in this file are all commented out by
 # default.  Usually they can be detected and built as dynamically

Modules/hashtable.c renamed to Python/hashtable.c

@@ -45,7 +45,7 @@
 */
 
 #include "Python.h"
-#include "hashtable.h"
+#include "../Modules/hashtable.h"
 
 #define HASHTABLE_MIN_SIZE 16
 #define HASHTABLE_HIGH 0.50