Add GDB Stub (ryubing/ryujinx!71)

See merge request ryubing/ryujinx!71

src/Ryujinx.HLE/Debugger/GdbSignal.cs

@@ -0,0 +1,15 @@
+namespace Ryujinx.HLE.Debugger
+{
+    enum GdbSignal
+    {
+        Zero = 0,
+        Int = 2,
+        Quit = 3,
+        Trap = 5,
+        Abort = 6,
+        Alarm = 14,
+        IO = 23,
+        XCPU = 24,
+        Unknown = 143
+    }
+}