Py2.3 does not automatically include eval.h in Python.h

Cython/Compiler/Builtin.py

@@ -166,6 +166,11 @@ proto = """
 static PyObject* __Pyx_PyRun(PyObject*, PyObject*, PyObject*);
 """,
 impl = '''
+#if PY_VERSION_HEX < 0x02040000
+#ifndef Py_EVAL_H
+#include "eval.h"
+#endif
+#endif
 static PyObject* __Pyx_PyRun(PyObject* o, PyObject* globals, PyObject* locals) {
     PyObject* result;
     PyObject* s = 0;