Added SDL_LockRect() and SDL_UnlockRect()

Incorporated XFree86 extension libraries into the source

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40293

include/SDL_video.h

@@ -531,6 +531,26 @@ extern DECLSPEC void SDL_FreeSurface(SDL_Surface *surface);
 extern DECLSPEC int SDL_LockSurface(SDL_Surface *surface);
 extern DECLSPEC void SDL_UnlockSurface(SDL_Surface *surface);
 
+/*
+ * SDL_LockRect() locks a portion of the surface designated by the 'rect'
+ * parameter, and saves the resulting pixels and pitch in the arguments.
+ * The rect will be clipped if it extends beyond the bounds of the surface
+ *
+ * This may be more efficient than a full lock if you are using a hardware
+ * surface and plan to make a few changes to small areas in the surface.
+ *
+ * While a rectangle is locked, no other lock or blit call may be called
+ * on the surface.  No operating system or library calls should be made
+ * between lock/unlock pairs, as critical system locks may be held during
+ * this time.
+ *
+ * After the surface is unlocked, the pixels pointer is no longer valid.
+ *
+ * SDL_LockRect() returns 0, or -1 if the surface couldn't be locked.
+ */
+extern DECLSPEC int SDL_LockRect(SDL_Surface *surface, SDL_Rect *rect, void **pixels, int *pitch);
+extern DECLSPEC void SDL_UnlockRect(SDL_Surface *surface);
+
 /*
  * Load a surface from a seekable SDL data source (memory or file.)
  * If 'freesrc' is non-zero, the source will be closed after being read.