Issue #27985: Implement PEP 526 -- Syntax for Variable Annotations.

Patch by Ivan Levkivskyi.
diff --git a/Include/symtable.h b/Include/symtable.h
index 1409cd9..b0259d6 100644
--- a/Include/symtable.h
+++ b/Include/symtable.h
@@ -91,6 +91,7 @@
 #define DEF_FREE 2<<4          /* name used but not defined in nested block */
 #define DEF_FREE_CLASS 2<<5    /* free variable from class's method */
 #define DEF_IMPORT 2<<6        /* assignment occurred via import */
+#define DEF_ANNOT 2<<7         /* this name is annotated */
 
 #define DEF_BOUND (DEF_LOCAL | DEF_PARAM | DEF_IMPORT)