Pass debug exceptions to winedos.

dlls/ntdll/signal_i386.c

@@ -1270,9 +1270,8 @@ void __wine_enter_vm86( CONTEXT *context )
         case VM86_TRAP: /* return due to DOS-debugger request */
             switch(VM86_ARG(res))
             {
-            case T_TRCTRAP:  /* Single-step exception */
+            case T_TRCTRAP:  /* Single-step exception, single step flag is cleared by raise_trap_exception */
                 rec.ExceptionCode = EXCEPTION_SINGLE_STEP;
-                context->EFlags &= ~0x100;  /* clear single-step flag */
                 break;
             case T_BPTFLT:   /* Breakpoint exception */
                 rec.ExceptionAddress = (char *)rec.ExceptionAddress - 1;  /* back up over the int3 instruction */

dlls/winedos/dosvm.c

@@ -557,6 +557,15 @@ static WINE_EXCEPTION_FILTER(exception_handler)
       ERR( "Protected mode STI caught by real mode handler!\n" );
     DOSVM_SendQueuedEvents(context);
     return EXCEPTION_CONTINUE_EXECUTION;
+  
+  case EXCEPTION_SINGLE_STEP:
+    ret = DOSVM_EmulateInterruptRM( context, 1 );
+    return ret ? EXCEPTION_CONTINUE_EXECUTION : EXCEPTION_EXECUTE_HANDLER;
+  
+  case EXCEPTION_BREAKPOINT:
+    ret = DOSVM_EmulateInterruptRM( context, 3 );
+    return ret ? EXCEPTION_CONTINUE_EXECUTION : EXCEPTION_EXECUTE_HANDLER;
+  
   }
   return EXCEPTION_CONTINUE_SEARCH;
 }