add screenshots folder if not exists

Vocaluxe/Lib/Draw/CDirect3D.cs

@@ -461,6 +461,8 @@ namespace Vocaluxe.Lib.Draw
         {
             string file = "Screenshot_";
             string path = Path.Combine(Environment.CurrentDirectory, CSettings.sFolderScreenshots);
+            if (!Directory.Exists(path))
+                Directory.CreateDirectory(path);
 
             int i = 0;
             while (File.Exists(Path.Combine(path, file + i.ToString("00000") + ".bmp")))

Vocaluxe/Lib/Draw/CDrawWinForm.cs

@@ -300,6 +300,8 @@ namespace Vocaluxe.Lib.Draw
         {
             string file = "Screenshot_";
             string path = Path.Combine(Environment.CurrentDirectory, CSettings.sFolderScreenshots);
+            if (!Directory.Exists(path))
+                Directory.CreateDirectory(path);
 
             int i = 0;
             while (File.Exists(Path.Combine(path, file + i.ToString("00000") + ".png")))

Vocaluxe/Lib/Draw/COpenGL.cs

@@ -556,6 +556,8 @@ namespace Vocaluxe.Lib.Draw
         {
             string file = "Screenshot_";
             string path = Path.Combine(Environment.CurrentDirectory, CSettings.sFolderScreenshots);
+            if (!Directory.Exists(path))
+                Directory.CreateDirectory(path);
 
             int i = 0;
             while (File.Exists(Path.Combine(path, file + i.ToString("00000") + ".bmp")))