python: Include <Python.h> first

Python is broken and requires that we include <Python.h> before all
other headers so it can make inadvisable definitions of
_POSIX_C_SOURCE and other things.  This wasn't a problem before, but a
recent change to glibc makes this necessary now.

See also a similar commit in nbdkit:
f924c3c34b

I also removed the -Wcast-align suppression as that is no longer
needed.

generator/python.ml

@@ -43,13 +43,6 @@ let rec generate_python_actions_h () =
 #include "guestfs.h"
 #include "guestfs-stringlists-utils.h"
 
-#define PY_SSIZE_T_CLEAN 1
-
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wcast-align"
-#include <Python.h>
-#pragma GCC diagnostic pop
-
 static inline guestfs_h *
 get_handle (PyObject *obj)
 {
@@ -117,7 +110,11 @@ extern char *guestfs_int_py_asstring (PyObject *obj);
 and generate_python_structs () =
   generate_header CStyle LGPLv2plus;
 
-  pr {|#include <config.h>
+  pr {|/* This must be included first. */
+#define PY_SSIZE_T_CLEAN 1
+#include <Python.h>
+
+#include <config.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -252,7 +249,11 @@ and generate_python_structs () =
 and generate_python_actions actions () =
   generate_header CStyle LGPLv2plus;
 
-  pr {|#include <config.h>
+  pr {|/* This must be included first. */
+#define PY_SSIZE_T_CLEAN 1
+#include <Python.h>
+
+#include <config.h>
 
 /* It is safe to call deprecated functions from this file. */
 #define GUESTFS_NO_WARN_DEPRECATED
@@ -523,7 +524,11 @@ and generate_python_actions actions () =
 and generate_python_module () =
   generate_header CStyle LGPLv2plus;
 
-  pr {|#include <config.h>
+  pr {|/* This must be included first. */
+#define PY_SSIZE_T_CLEAN 1
+#include <Python.h>
+
+#include <config.h>
 
 #include <stdio.h>
 #include <stdlib.h>

python/handle.c

@@ -22,6 +22,10 @@
  * F<python/actions-*.c>).
  */
 
+/* This must be included first. */
+#define PY_SSIZE_T_CLEAN 1
+#include <Python.h>
+
 #include <config.h>
 
 #include <stdio.h>