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/opcode.h

@@ -1,12 +1,10 @@
-/* Auto-generated by Tools/scripts/generate_opcode_h.py */
 #ifndef Py_OPCODE_H
 #define Py_OPCODE_H
-#ifdef __cplusplus
-extern "C" {
-#endif
+COSMOPOLITAN_C_START_
+/* clang-format off */
+/* Auto-generated by Tools/scripts/generate_opcode_h.py */
 
-
-    /* Instruction opcodes for compiled code */
+/* Instruction opcodes for compiled code */
 #define POP_TOP                   1
 #define ROT_TWO                   2
 #define ROT_THREE                 3
@@ -140,7 +138,5 @@ enum cmp_op {PyCmp_LT=Py_LT, PyCmp_LE=Py_LE, PyCmp_EQ=Py_EQ, PyCmp_NE=Py_NE,
 
 #define HAS_ARG(op) ((op) >= HAVE_ARGUMENT)
 
-#ifdef __cplusplus
-}
-#endif
+COSMOPOLITAN_C_END_
 #endif /* !Py_OPCODE_H */