[CPyCppyy] Rename PyInit_libcppyy to Init for ROOT module split [ROOT-patch]

Source: ROOT-master

ROOT runs CPyCppyy and libROOTPythonizations as two shared libs
that under the same libcppyy Python extension module. The real PyInit_libcppyy
lives in libROOTPythonizations and calls CPyCppyy::Init() to start the extension.

Author: aaronj0

bindings/pyroot/cppyy/CPyCppyy/src/CPyCppyyModule.cxx

@@ -1089,7 +1089,7 @@ static struct PyModuleDef moduledef = {
 namespace CPyCppyy {
 
 //----------------------------------------------------------------------------
-extern "C" PyObject* PyInit_libcppyy()
+PyObject* Init()
 {
 // Initialization of extension module libcppyy.