Bug #235651 --> More installer work for Thunderbird. Add a .ico file for mail just like we have for browser

toolkit/mozapps/installer/windows/wizard/setuprsc/setuprsc.h

@@ -14,6 +14,7 @@
 #define IDS_MSG_RETRIEVE_INSTALLINI     11
 #define IDI_SETUP                       105
 #define IDI_BROWSER                     106
+#define IDI_MAIL                        107
 #define IDB_BITMAP_WELCOME              108
 #define DLG_MESSAGE                     110
 #define IDB_BITMAP_BANNER               114

toolkit/mozapps/installer/windows/wizard/setuprsc/setuprsc.rc

@@ -382,6 +382,7 @@ END
 // remains consistent on all systems.
 IDI_SETUP               ICON    DISCARDABLE     "setup.ico"
 IDI_BROWSER             ICON    DISCARDABLE     "browser.ico"
+IDI_MAIL                ICON    DISCARDABLE     "mail.ico"
 
 /////////////////////////////////////////////////////////////////////////////
 //