[14-08-2002] Eliminate use of Draw_Init
  Now the library doesn't need Draw_Init anymore!!
  Every function has a default function pointer to a init function that
  change all the primitives functions pointers in the library, and then call 
  the correct function. Later calls to the primitives will use the correct 
  function pointer. Code already using Draw_Init can do...

  #include "SDL_draw.h"
  #define Draw_Init do{ }while(0)

  ...to fix this (maintaining compatibility) and use the new library.
  
[13-08-2002] Lock and Unlock code for threading
  Now all the primitives have a SDL_LockSurface and SDL_UnlockSurface for
  correct behavior on multithreaded code.
  
