Use GROWABLE_BIT_SET instead of IS_GROWABLE in data.table workaround.

git-svn-id: https://svn.r-project.org/R/trunk@89044 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

src/main/duplicate.c

@@ -41,7 +41,7 @@
  *  the value duplicated.  */
 
 #define COPY_TRUELENGTH(to, from) do {			\
-	if (! IS_GROWABLE(from))			\
+	if (! GROWABLE_BIT_SET(from))			\
 	    SET_TRUELENGTH(to, XTRUELENGTH(from));	\
     } while (0)