patch 9.0.0936: wrong type for "isunnamed" returned by getreginfo()

Problem:    Wrong type for "isunnamed" returned by getreginfo().
Solution:   Use VAR_BOOL instead of VAR_SPECIAL. (closes #11598)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index e4f28ed..112a2e7 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -8415,7 +8415,7 @@
 
 	if (item != NULL)
 	{
-	    item->di_tv.v_type = VAR_SPECIAL;
+	    item->di_tv.v_type = VAR_BOOL;
 	    item->di_tv.vval.v_number = regname == buf[0]
 						      ? VVAL_TRUE : VVAL_FALSE;
 	    (void)dict_add(dict, item);