fix syntax

Author: mythz

src/ServiceStack.Text/PclExport.cs

@@ -479,7 +479,7 @@ public virtual Task WriteAndFlushAsync(Stream stream, byte[] bytes)
 #if !SL5
             return stream.WriteAsync(bytes, 0, bytes.Length)
                 .ContinueWith(t => stream.FlushAsync());
-#elif
+#else
             stream.Write(bytes, 0, bytes.Length);
             stream.Flush();
 #endif