ntdll: Ignore ExceptionFlags changes done by exception handlers.

Fixes exceptions rethrowing in 64-bit .Net.

Signed-off-by: Piotr Caban <piotr@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>

dlls/ntdll/signal_x86_64.c

@@ -2390,6 +2390,7 @@ static DWORD call_handler( EXCEPTION_RECORD *rec, CONTEXT *context, DISPATCHER_C
     res = dispatch->LanguageHandler( rec, (void *)dispatch->EstablisherFrame, context, dispatch );
     TRACE( "handler at %p returned %u\n", dispatch->LanguageHandler, res );
 
+    rec->ExceptionFlags &= EH_NONCONTINUABLE;
     __wine_pop_frame( &frame );
     return res;
 }