mainform: playback: Move song track position to mouse position on click

Allows for smoother track seeking when the song is paused.
For now, we keep the current behavior of disabling all track seeking while the song is playing.

BAKKA-Editor/MainForm.Designer.cs

@@ -753,6 +753,7 @@
             this.songTrackBar.TabIndex = 2;
             this.songTrackBar.TickStyle = System.Windows.Forms.TickStyle.None;
             this.songTrackBar.ValueChanged += new System.EventHandler(this.songTrackBar_ValueChanged);
+            this.songTrackBar.MouseDown += new System.Windows.Forms.MouseEventHandler(this.songTrackBar_MouseDown);
             // 
             // selectSongButton
             // 

BAKKA-Editor/MainForm.cs

@@ -1976,5 +1976,12 @@ namespace BAKKA_Editor
                     File.Delete(file);
             }
         }
+
+        private void songTrackBar_MouseDown(object sender, MouseEventArgs e)
+        {
+            float val = ((float)e.Location.X / (float)songTrackBar.Width) *
+                        (songTrackBar.Maximum - songTrackBar.Minimum);
+            songTrackBar.Value = (int)val;
+        }
     }
 }