Simon has reminded me _why_ menu identifiers were spaced every sixteen, so

let's add a comment so that we don't forget again. Source:
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/keyboardaccelerators/keyboardacceleratorreference/keyboardacceleratormessages/wm_syscommand.asp>

[originally from svn r4732]

pageant.c

@@ -33,6 +33,11 @@
  */
 #define AGENT_MAX_MSGLEN  8192
 
+/* From MSDN: In the WM_SYSCOMMAND message, the four low-order bits of
+ * wParam are used by Windows, and should be masked off, so we shouldn't
+ * attempt to store information in them. Hence all these identifiers have
+ * the low 4 bits clear. */
+
 #define IDM_CLOSE    0x0010
 #define IDM_VIEWKEYS 0x0020
 #define IDM_ADDKEY   0x0030

window.c

@@ -22,6 +22,11 @@
 #include <richedit.h>
 #include <mmsystem.h>
 
+/* From MSDN: In the WM_SYSCOMMAND message, the four low-order bits of
+ * wParam are used by Windows, and should be masked off, so we shouldn't
+ * attempt to store information in them. Hence all these identifiers have
+ * the low 4 bits clear. */
+
 #define IDM_SHOWLOG   0x0010
 #define IDM_NEWSESS   0x0020
 #define IDM_DUPSESS   0x0030