Merged r5016:5017 from branches/SDL-1.2: PS2 DMA mapping fix.

I assume this video target is slated for removal in 1.3, but I merged this,
just in case.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%404377

src/video/ps2gs/SDL_gsyuv.c

@@ -184,7 +184,7 @@ GS_CreateYUVOverlay(_THIS, int width, int height, Uint32 format,
 
     /* Allocate a DMA area for pixel conversion */
     bpp = this->screen->format->BytesPerPixel;
-    map_offset = (mapped_len + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
+    map_offset = (mapped_len + (sysconf(_SC_PAGESIZE) - 1)) & ~(sysconf(_SC_PAGESIZE) - 1);
     hwdata->dma_len = hwdata->macroblocks * (16 * 16 + 8 * 8 + 8 * 8) +
         width * height * bpp +
         hwdata->macroblocks * (16 * sizeof(long long)) +