Adding overload for SDL_LockTexture to allow IntPtr.Zero in the "rect" parameter. SDL documentation states that passing NULL for this value will lock the entire texture."
Forgot to save the file before pushing. Ugh.
Merge pull request #37 from babelshift/sdl-locktexture-allow-null-rect

Adding overload for SDL_LockTexture to allow IntPtr.Zero for "rect" parameter