external/python3: Avoid misaligned-pointer-use

...when generating Python/deepfreeze/deepfreeze.c during the build of
ExternalProject_python3 after 5052448 "Python:
upgrade to 3.11.11 (master only)",

> Objects/dictobject.c:1500:40: runtime error: load of misaligned address 0x555853494d81 for type 'PyDictUnicodeEntry *', which requires 8 byte alignment
> 0x555853494d81: note: pointer points here
>  00 00 00  ff ff ff ff ff ff ff ff  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00
>               ^
>  #0 in dictresize at workdir/UnpackedTarball/python3/Objects/dictobject.c:1500:21
>  #1 in dict_merge at workdir/UnpackedTarball/python3/Objects/dictobject.c:2880:17
>  #2 in _PyDict_MergeEx at workdir/UnpackedTarball/python3/Objects/dictobject.c:3003:12
>  #3 in _PyEval_EvalFrameDefault at workdir/UnpackedTarball/python3/Python/ceval.c:3432:17
>  #4 in _PyEval_EvalFrame at workdir/UnpackedTarball/python3/./Include/internal/pycore_ceval.h:73:16
>  #5 in _PyEval_Vector at workdir/UnpackedTarball/python3/Python/ceval.c:6434:24
>  #6 in _PyFunction_Vectorcall at workdir/UnpackedTarball/python3/Objects/call.c:393:16
>  #7 in _PyObject_FastCallDictTstate at workdir/UnpackedTarball/python3/Objects/call.c:141:15
>  #8 in _PyObject_Call_Prepend at workdir/UnpackedTarball/python3/Objects/call.c:482:24
>  #9 in slot_tp_init at workdir/UnpackedTarball/python3/Objects/typeobject.c:7855:15
>  #10 in type_call at workdir/UnpackedTarball/python3/Objects/typeobject.c:1103:19
>  #11 in _PyObject_MakeTpCall at workdir/UnpackedTarball/python3/Objects/call.c:214:18
>  #12 in _PyObject_VectorcallTstate at workdir/UnpackedTarball/python3/./Include/internal/pycore_call.h:90:16
>  #13 in PyObject_Vectorcall at workdir/UnpackedTarball/python3/Objects/call.c:299:12
>  #14 in _PyEval_EvalFrameDefault at workdir/UnpackedTarball/python3/Python/ceval.c:4769:23
>  #15 in _PyEval_EvalFrame at workdir/UnpackedTarball/python3/./Include/internal/pycore_ceval.h:73:16
>  #16 in _PyEval_Vector at workdir/UnpackedTarball/python3/Python/ceval.c:6434:24
>  #17 in PyEval_EvalCode at workdir/UnpackedTarball/python3/Python/ceval.c:1148:21
>  #18 in run_eval_code_obj at workdir/UnpackedTarball/python3/Python/pythonrun.c:1741:9
>  #19 in run_mod at workdir/UnpackedTarball/python3/Python/pythonrun.c:1762:19
>  #20 in pyrun_file at workdir/UnpackedTarball/python3/Python/pythonrun.c:1657:15
>  #21 in _PyRun_SimpleFileObject at workdir/UnpackedTarball/python3/Python/pythonrun.c:440:13
>  #22 in _PyRun_AnyFileObject at workdir/UnpackedTarball/python3/Python/pythonrun.c:79:15
>  #23 in pymain_run_file_obj at workdir/UnpackedTarball/python3/Modules/main.c:360:15
>  #24 in pymain_run_file at workdir/UnpackedTarball/python3/Modules/main.c:379:15
>  #25 in pymain_run_python at workdir/UnpackedTarball/python3/Modules/main.c:605:21
>  #26 in Py_RunMain at workdir/UnpackedTarball/python3/Modules/main.c:684:5
>  #27 in main at workdir/UnpackedTarball/python3/Programs/_bootstrap_python.c:109:12

Change-Id: I0bacef11b5874bca6104516a206076a0505528ed
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/180037
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <[email protected]>

external/python3/ubsan.patch.0

@@ -30,6 +30,17 @@
  all_ins(PyObject *m)
  {
  #ifdef F_OK
+--- Objects/dictobject.c
++++ Objects/dictobject.c
+@@ -1497,7 +1497,7 @@
+             if (unicode) { // combined unicode -> combined unicode
+                 PyDictUnicodeEntry *newentries = DK_UNICODE_ENTRIES(mp->ma_keys);
+                 if (oldkeys->dk_nentries == numentries && mp->ma_keys->dk_kind == DICT_KEYS_UNICODE) {
+-                    memcpy(newentries, oldentries, numentries * sizeof(PyDictUnicodeEntry));
++                    memcpy(newentries, (void *) oldentries, numentries * sizeof(PyDictUnicodeEntry));
+                 }
+                 else {
+                     PyDictUnicodeEntry *ep = oldentries;
 --- Objects/listobject.c
 +++ Objects/listobject.c
 @@ -554,7 +554,7 @@