gh-129666: Add C11/C++11 to docs and -pedantic-errors to GCC/clang test_c[pp]ext tests (GH-130692)

Disable pedantic check for c++03 (unlimited API)

Also add a check for c++03 *limited* API, which passes in pedantic mode
after removing a comma in the `PySendResult` declaration, and allowing
`long long`.

Include/object.h

@@ -683,7 +683,7 @@ PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 typedef enum {
     PYGEN_RETURN = 0,
     PYGEN_ERROR = -1,
-    PYGEN_NEXT = 1,
+    PYGEN_NEXT = 1
 } PySendResult;
 #endif