Import internal CPython frame header file in Python 3.11 (GH-4667)

In https://github.com/python/cpython/pull/31530
https://bugs.python.org/issue46836

the `_frame` struct was moved to an internal header, however the public API is
primarily read-only, and Cython needs to build PyFrameObjects so still import
the internal headers.

Also sets the Py_BUILD_CORE define for py311a6, trying to restrict it to the frame header.

Cython/Utility/Coroutine.c

@@ -490,6 +490,12 @@ static int __pyx_Generator_init(void); /*proto*/
 
 #include <structmember.h>
 #include <frameobject.h>
+#if PY_VERSION_HEX >= 0x030b00a6
+  #ifndef Py_BUILD_CORE
+    #define Py_BUILD_CORE 1
+  #endif
+  #include "internal/pycore_frame.h"
+#endif
 
 #define __Pyx_Coroutine_Undelegate(gen) Py_CLEAR((gen)->yieldfrom)
 

Cython/Utility/Exceptions.c

@@ -705,6 +705,12 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
 #include "compile.h"
 #include "frameobject.h"
 #include "traceback.h"
+#if PY_VERSION_HEX >= 0x030b00a6
+  #ifndef Py_BUILD_CORE
+    #define Py_BUILD_CORE 1
+  #endif
+  #include "internal/pycore_frame.h"
+#endif
 
 static PyCodeObject* __Pyx_CreateCodeObjectForTraceback(
             const char *funcname, int c_line,

Cython/Utility/ObjectHandling.c

@@ -1996,6 +1996,13 @@ static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args,
   static size_t __pyx_pyframe_localsplus_offset = 0;
 
   #include "frameobject.h"
+#if PY_VERSION_HEX >= 0x030b00a6
+  #ifndef Py_BUILD_CORE
+    #define Py_BUILD_CORE 1
+  #endif
+  #include "internal/pycore_frame.h"
+#endif
+
   // This is the long runtime version of
   //     #define __Pyx_PyFrame_GetLocalsplus(frame)  ((frame)->f_localsplus)
   // offsetof(PyFrameObject, f_localsplus) differs between regular C-Python and Stackless Python.

Cython/Utility/Profile.c

@@ -38,6 +38,12 @@
   #include "compile.h"
   #include "frameobject.h"
   #include "traceback.h"
+#if PY_VERSION_HEX >= 0x030b00a6
+  #ifndef Py_BUILD_CORE
+    #define Py_BUILD_CORE 1
+  #endif
+  #include "internal/pycore_frame.h"
+#endif
 
   #if CYTHON_PROFILE_REUSE_FRAME
     #define CYTHON_FRAME_MODIFIER static