The correct icon name is "dialog-information", not "dialog-info"

Spec here:
http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html

gtk/Makefile.am

@@ -1018,7 +1018,7 @@ STOCK_ICONS = \
 	stock-icons/16/format-indent-more-ltr.png 	\
 	stock-icons/16/format-indent-more-rtl.png 	\
 	stock-icons/16/gtk-index.png 			\
-	stock-icons/16/dialog-info.png 			\
+	stock-icons/16/dialog-information.png		\
 	stock-icons/16/go-jump-ltr.png 			\
 	stock-icons/16/go-jump-rtl.png 			\
 	stock-icons/16/format-justify-center.png 	\
@@ -1123,7 +1123,7 @@ STOCK_ICONS = \
 	stock-icons/24/format-indent-more-ltr.png 	\
 	stock-icons/24/format-indent-more-rtl.png 	\
 	stock-icons/24/gtk-index.png  			\
-	stock-icons/24/dialog-info.png 			\
+	stock-icons/24/dialog-information.png		\
 	stock-icons/24/format-text-italic.png 		\
 	stock-icons/24/go-jump-ltr.png 			\
 	stock-icons/24/go-jump-rtl.png 			\
@@ -1193,7 +1193,7 @@ STOCK_ICONS = \
 	stock-icons/32/gtk-dnd.png 			\
 	stock-icons/48/dialog-password.png 		\
 	stock-icons/48/dialog-error.png 		\
-	stock-icons/48/dialog-info.png 			\
+	stock-icons/48/dialog-information.png		\
 	stock-icons/48/dialog-question.png 		\
 	stock-icons/48/dialog-warning.png
 

gtk/gtkiconfactory.c

@@ -408,7 +408,7 @@ get_default_icons (GtkIconFactory *factory)
 
   register_stock_icon (factory, GTK_STOCK_DIALOG_AUTHENTICATION, "dialog-password");
   register_stock_icon (factory, GTK_STOCK_DIALOG_ERROR, "dialog-error");
-  register_stock_icon (factory, GTK_STOCK_DIALOG_INFO, "dialog-info");
+  register_stock_icon (factory, GTK_STOCK_DIALOG_INFO, "dialog-information");
   register_stock_icon (factory, GTK_STOCK_DIALOG_QUESTION, "dialog-question");
   register_stock_icon (factory, GTK_STOCK_DIALOG_WARNING, "dialog-warning");
   register_stock_icon (factory, GTK_STOCK_DND, GTK_STOCK_DND);
@@ -439,7 +439,7 @@ get_default_icons (GtkIconFactory *factory)
   register_stock_icon (factory, GTK_STOCK_HARDDISK, "drive-harddisk");
   register_stock_icon (factory, GTK_STOCK_HELP, "help-contents");
   register_stock_icon (factory, GTK_STOCK_HOME, "go-home");
-  register_stock_icon (factory, GTK_STOCK_INFO, "dialog-info");
+  register_stock_icon (factory, GTK_STOCK_INFO, "dialog-information");
   register_bidi_stock_icon (factory, GTK_STOCK_JUMP_TO, "go-jump");
   register_bidi_stock_icon (factory, GTK_STOCK_GOTO_LAST, "go-last");
   register_bidi_stock_icon (factory, GTK_STOCK_GO_BACK, "go-previous");