patch 7.4.1499

Problem:    No error message when :packadd does not find anything.
Solution:   Add an error message. (Hirohito Higashi)

src/globals.h

@@ -1577,6 +1577,7 @@ EXTERN char_u e_notset[]	INIT(= N_("E764: Option '%s' is not set"));
 #ifndef FEAT_CLIPBOARD
 EXTERN char_u e_invalidreg[]    INIT(= N_("E850: Invalid register name"));
 #endif
+EXTERN char_u e_dirnotf[]	INIT(= N_("E919: Directory not found in '%s': \"%s\""));
 
 #ifdef MACOS_X_UNIX
 EXTERN short disallow_gui	INIT(= FALSE);