Add new "Modal form" opcode, also add sample code to use it.

Signed-off-by: ydong10
Reviewed-by: lgao4







git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11764 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/DriverSampleDxe/DriverSample.c

@@ -1502,6 +1502,7 @@ DriverCallback (
       break;
 
     case 0x1241:
+    case 0x1246:
       //
       // User press "Submit current form and Exit now", request Browser to submit current form and exit
       //
@@ -1523,6 +1524,7 @@ DriverCallback (
       break;
 
     case 0x1244:
+    case 0x1245:
       //
       // User press "Discard current form and Exit now", request Browser to discard the uncommitted data and exit.
       //