Complete rewrite of bsd IClient (#460)

This should provide accurate behaviours.
This implementation has been tested with ftpd and libtransistor bsd tests.

This implementation lacks OOB support.

Ryujinx.HLE/HOS/Services/Bsd/PollEvent.cs

@@ -0,0 +1,28 @@
+namespace Ryujinx.HLE.HOS.Services.Bsd
+{
+    class PollEvent
+    {
+        public enum EventTypeMask
+        {
+            Input        = 1,
+            UrgentInput  = 2,
+            Output       = 4,
+            Error        = 8,
+            Disconnected = 0x10,
+            Invalid      = 0x20,
+        }
+
+        public int           SocketFd     { get; private set; }
+        public BsdSocket     Socket       { get; private set; }
+        public EventTypeMask InputEvents  { get; private set; }
+        public EventTypeMask OutputEvents { get; private set; }
+
+        public PollEvent(int SocketFd, BsdSocket Socket, EventTypeMask InputEvents, EventTypeMask OutputEvents)
+        {
+            this.SocketFd     = SocketFd;
+            this.Socket       = Socket;
+            this.InputEvents  = InputEvents;
+            this.OutputEvents = OutputEvents;
+        }
+    }
+}