Move the following files from Modules/_testcapi/ to
Modules/_testlimitedcapi/:
* bytearray.c
* bytes.c
* pyos.c
* sys.c
Changes:
* Replace PyBytes_AS_STRING() with PyBytes_AsString().
* Replace PyBytes_GET_SIZE() with PyBytes_Size().
* Update related test_capi tests.
* Copy Modules/_testcapi/util.h to Modules/_testlimitedcapi/util.h.
* Move existing tests for PySys_GetObject() and PySys_SetObject() into
specialized files.
* Add test for PySys_GetXOptions() using _testcapi.
* Add tests for PySys_FormatStdout(), PySys_FormatStderr(),
PySys_WriteStdout() and PySys_WriteStderr() using ctypes.
Serhiy Storchaka