bpo-29936: fix typo __GNU*C*_MINOR__ (#878)

Author: niklasf

Include/pymacro.h

@@ -53,7 +53,7 @@
 
    Requires at GCC 3.1+ */
 #if (defined(__GNUC__) && !defined(__STRICT_ANSI__) && \
-    (((__GNUC__ == 3) && (__GNU_MINOR__ >= 1)) || (__GNUC__ >= 4)))
+    (((__GNUC__ == 3) && (__GNUC_MINOR__ >= 1)) || (__GNUC__ >= 4)))
 /* Two gcc extensions.
    &a[0] degrades to a pointer: a different type from an array */
 #define Py_ARRAY_LENGTH(array) \