patch 8.2.0517: Vim9: cannot separate "func" and "func(): void"

Problem:    Vim9: cannot separate "func" and "func(): void".
Solution:   Use VAR_ANY for "any" and VAR_UNKNOWN for "no type".
diff --git a/src/structs.h b/src/structs.h
index 4a51281..46e2701 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1321,8 +1321,9 @@
 
 typedef enum
 {
-    VAR_UNKNOWN = 0,	// not set, also used for "any" type
-    VAR_VOID,		// no value
+    VAR_UNKNOWN = 0,	// not set, any type or "void" allowed
+    VAR_ANY,		// used for "any" type
+    VAR_VOID,		// no value (function not returning anything)
     VAR_BOOL,		// "v_number" is used: VVAL_TRUE or VVAL_FALSE
     VAR_SPECIAL,	// "v_number" is used: VVAL_NULL or VVAL_NONE
     VAR_NUMBER,		// "v_number" is used