Perform build and magnum tuning

Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.

third_party/python/Include/pyarena.h

@@ -1,64 +1,56 @@
-/* An arena-like memory interface for the compiler.
- */
-
 #ifndef Py_LIMITED_API
 #ifndef Py_PYARENA_H
 #define Py_PYARENA_H
+COSMOPOLITAN_C_START_
+/* clang-format off */
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+typedef struct _arena PyArena;
 
-  typedef struct _arena PyArena;
+/* PyArena_New() and PyArena_Free() create a new arena and free it,
+   respectively.  Once an arena has been created, it can be used
+   to allocate memory via PyArena_Malloc().  Pointers to PyObject can
+   also be registered with the arena via PyArena_AddPyObject(), and the
+   arena will ensure that the PyObjects stay alive at least until
+   PyArena_Free() is called.  When an arena is freed, all the memory it
+   allocated is freed, the arena releases internal references to registered
+   PyObject*, and none of its pointers are valid.
+   XXX (tim) What does "none of its pointers are valid" mean?  Does it
+   XXX mean that pointers previously obtained via PyArena_Malloc() are
+   XXX no longer valid?  (That's clearly true, but not sure that's what
+   XXX the text is trying to say.)
 
-  /* PyArena_New() and PyArena_Free() create a new arena and free it,
-     respectively.  Once an arena has been created, it can be used
-     to allocate memory via PyArena_Malloc().  Pointers to PyObject can
-     also be registered with the arena via PyArena_AddPyObject(), and the
-     arena will ensure that the PyObjects stay alive at least until
-     PyArena_Free() is called.  When an arena is freed, all the memory it
-     allocated is freed, the arena releases internal references to registered
-     PyObject*, and none of its pointers are valid.
-     XXX (tim) What does "none of its pointers are valid" mean?  Does it
-     XXX mean that pointers previously obtained via PyArena_Malloc() are
-     XXX no longer valid?  (That's clearly true, but not sure that's what
-     XXX the text is trying to say.)
+   PyArena_New() returns an arena pointer.  On error, it
+   returns a negative number and sets an exception.
+   XXX (tim):  Not true.  On error, PyArena_New() actually returns NULL,
+   XXX and looks like it may or may not set an exception (e.g., if the
+   XXX internal PyList_New(0) returns NULL, PyArena_New() passes that on
+   XXX and an exception is set; OTOH, if the internal
+   XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
+   XXX an exception is not set in that case).
+*/
+PyAPI_FUNC(PyArena *) PyArena_New(void);
+PyAPI_FUNC(void) PyArena_Free(PyArena *);
 
-     PyArena_New() returns an arena pointer.  On error, it
-     returns a negative number and sets an exception.
-     XXX (tim):  Not true.  On error, PyArena_New() actually returns NULL,
-     XXX and looks like it may or may not set an exception (e.g., if the
-     XXX internal PyList_New(0) returns NULL, PyArena_New() passes that on
-     XXX and an exception is set; OTOH, if the internal
-     XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
-     XXX an exception is not set in that case).
-  */
-  PyAPI_FUNC(PyArena *) PyArena_New(void);
-  PyAPI_FUNC(void) PyArena_Free(PyArena *);
+/* Mostly like malloc(), return the address of a block of memory spanning
+ * `size` bytes, or return NULL (without setting an exception) if enough
+ * new memory can't be obtained.  Unlike malloc(0), PyArena_Malloc() with
+ * size=0 does not guarantee to return a unique pointer (the pointer
+ * returned may equal one or more other pointers obtained from
+ * PyArena_Malloc()).
+ * Note that pointers obtained via PyArena_Malloc() must never be passed to
+ * the system free() or realloc(), or to any of Python's similar memory-
+ * management functions.  PyArena_Malloc()-obtained pointers remain valid
+ * until PyArena_Free(ar) is called, at which point all pointers obtained
+ * from the arena `ar` become invalid simultaneously.
+ */
+PyAPI_FUNC(void *) PyArena_Malloc(PyArena *, size_t size);
 
-  /* Mostly like malloc(), return the address of a block of memory spanning
-   * `size` bytes, or return NULL (without setting an exception) if enough
-   * new memory can't be obtained.  Unlike malloc(0), PyArena_Malloc() with
-   * size=0 does not guarantee to return a unique pointer (the pointer
-   * returned may equal one or more other pointers obtained from
-   * PyArena_Malloc()).
-   * Note that pointers obtained via PyArena_Malloc() must never be passed to
-   * the system free() or realloc(), or to any of Python's similar memory-
-   * management functions.  PyArena_Malloc()-obtained pointers remain valid
-   * until PyArena_Free(ar) is called, at which point all pointers obtained
-   * from the arena `ar` become invalid simultaneously.
-   */
-  PyAPI_FUNC(void *) PyArena_Malloc(PyArena *, size_t size);
-
-  /* This routine isn't a proper arena allocation routine.  It takes
-   * a PyObject* and records it so that it can be DECREFed when the
-   * arena is freed.
-   */
-  PyAPI_FUNC(int) PyArena_AddPyObject(PyArena *, PyObject *);
-
-#ifdef __cplusplus
-}
-#endif
+/* This routine isn't a proper arena allocation routine.  It takes
+ * a PyObject* and records it so that it can be DECREFed when the
+ * arena is freed.
+ */
+PyAPI_FUNC(int) PyArena_AddPyObject(PyArena *, PyObject *);
 
+COSMOPOLITAN_C_END_
 #endif /* !Py_PYARENA_H */
 #endif /* Py_LIMITED_API */