sdl-sopwith-2.1.0

Bug fixes and changes in this version:

• libm is included as a dependency when needed (thanks slicer69).
• No error is printed if the config file doesn't exist (thanks Kenneth
  Pronovici).
• The screen is now redrawn properly when in menus and the window is uncovered
  or resized (thanks Kenneth Pronovici).
• Some potential crashes were fixed when near the edges of the map.
• Some of the code has been refactored to centralize how levels are defined. In
  the future this will help to support custom levels.

Documentation changes:

• Build instructions were clarified (thanks Kenneth Pronovici).
• Better documentation of novice mode was added to the manpage (thanks Kenneth
  Pronovici).
• References to the -p argument were removed from the manpage and the help text
  (thanks Kenneth Pronovici).