Added Mono toolchain finding support code.

src/Core/Toolchains/MonoToolchain.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace CppSharp
+{
+    public static class MonoToolchain
+    {
+        public static string FindMonoPath()
+        {
+            if (Platform.IsWindows)
+                return @"C:\\Program Files (x86)\\Mono";
+            else if (Platform.IsMacOS)
+                return "/Library/Frameworks/Mono.framework/Versions/Current";
+
+            throw new NotImplementedException();
+        }
+
+        public static string FindCSharpCompilerPath()
+        {
+            if (Platform.IsWindows)
+            {
+                List<ToolchainVersion> versions;
+                if (!MSVCToolchain.GetMSBuildSdks(out versions))
+                    throw new Exception("Could not find MSBuild SDK paths");
+
+                var sdk = versions.Last();
+
+                return Path.Combine(sdk.Directory, "csc.exe");
+            }
+
+            return Path.Combine(FindMonoPath(), "bin", "mcs.exe");
+        }
+    }
+}