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/BsdIoctl.cs

@@ -0,0 +1,7 @@
+namespace Ryujinx.HLE.HOS.Services.Bsd
+{
+    enum BsdIoctl
+    {
+        AtMark = 0x40047307,
+    }
+}