message: Remove explicit empty FontManager constructor and destructor
diff: class FontManager
  {
  public:
  - /**
  - * C'tor
  - */
  - FontManager()
  - {}
  -
  - /**
  - * D'tor
  - */
  - ~FontManager()
  - {
  - }
  -
  /**
  * Gets a pointer to a NAS2D::Font object given a filename on disk
  * and a size in points.
  