Fix PY_HEX_VERSION -> PY_VERSION_HEX (GH-3071)

CHANGES.rst

@@ -360,7 +360,7 @@ Features added
   In this case, it is also automatically mapped to ``%r`` in Python 2.x.
 
 * New C macro ``CYTHON_HEX_VERSION`` to access Cython's version in the same style as
-  ``PY_HEX_VERSION``.
+  ``PY_VERSION_HEX``.
 
 * Constants in ``libc.math`` are now declared as ``const`` to simplify their handling.
 

Cython/Utils.py

@@ -442,7 +442,7 @@ def raise_error_if_module_name_forbidden(full_module_name):
 
 def build_hex_version(version_string):
     """
-    Parse and translate '4.3a1' into the readable hex representation '0x040300A1' (like PY_HEX_VERSION).
+    Parse and translate '4.3a1' into the readable hex representation '0x040300A1' (like PY_VERSION_HEX).
     """
     # First, parse '4.12a1' into [4, 12, 0, 0xA01].
     digits = []