Update CPy.h

Author: BobTheBuidler

mypyc/lib-rt/CPy.h

@@ -752,6 +752,7 @@ bool CPyStr_IsTrue(PyObject *obj);
 Py_ssize_t CPyStr_Size_size_t(PyObject *str);
 PyObject *CPy_Decode(PyObject *obj, PyObject *encoding, PyObject *errors);
 PyObject *CPy_Encode(PyObject *obj, PyObject *encoding, PyObject *errors);
+Py_ssize_t CPyStr_Count(PyObject *unicode, PyObject *substring, Py_ssize_t start);
 CPyTagged CPyStr_Ord(PyObject *obj);