Apply suggestions from code review

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: pablogsal

Include/pymacro.h

@@ -12,9 +12,11 @@
 
 // static_assert is defined in glibc from version 2.16. Before it requires
 // compiler support (gcc >= 4.6) and is called _Static_assert.
+// In C++ 11 static_assert is a keyword, redefining is undefined behaviour.
 #if (defined(__GLIBC__) \
      && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ <= 16)) \
-     && !defined(static_assert) && !(defined(__cplusplus) && __cplusplus >= 201103L))
+     && !(defined(__cplusplus) && __cplusplus >= 201103L) \
+     && !defined(static_assert))
 #  define static_assert _Static_assert
 #endif