bpo-35081: Move accu.h to Include/internal/pycore_accu.h (GH-10271)
The accu.h header is no longer part of the Python C API: it has been
moved to the "internal" headers which are restricted to Python
itself.
Replace #include "accu.h" with #include "pycore_accu.h".
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index 5a03715..793fa1e 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -1,7 +1,7 @@
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "structmember.h"
-#include "accu.h"
+#include "pycore_accu.h"
#include "_iomodule.h"
/* Implementation note: the buffer is always at least one character longer