msgs: One msgWriteln with optional flags

Instead of msgWriteln, outWriteln and stdoutWriteln doing essentially the same.

compiler/vm.nim

@@ -811,13 +811,13 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcEcho:
       let rb = instr.regB
       if rb == 1:
-        stdoutWriteln(regs[ra].node.strVal)
+        msgWriteln(regs[ra].node.strVal, {msgStdout})
       else:
         var outp = ""
         for i in ra..ra+rb-1:
           #if regs[i].kind != rkNode: debug regs[i]
           outp.add(regs[i].node.strVal)
-        stdoutWriteln(outp)
+        msgWriteln(outp, {msgStdout})
     of opcContainsSet:
       decodeBC(rkInt)
       regs[ra].intVal = ord(inSet(regs[rb].node, regs[rc].regToNode))