add SDL2 samples

sdl/DownloadLibrary.ps1

@@ -0,0 +1,14 @@
+Write-Host("Downloading library")
+$workingPath = (Get-Location).path
+$clnt = new-object System.Net.WebClient
+$url = "http://libsdl.org/release/SDL2-devel-2.0.1-VC.zip"
+$file = $workingPath + "\SDL2-devel-2.0.1-VC.zip"
+$clnt.DownloadFile($url,$file)
+
+Write-Host("Unzip the file to local directory")
+$shell_app=new-object -com shell.application 
+$zip_file = $shell_app.namespace($file) 
+$destination = $shell_app.namespace($workingPath) 
+$destination.Copyhere($zip_file.items())
+
+Write-Host("Done")