PROVIDE THE PROOF FOR MEMORY REDUCION

provide the proof for memory reduction, detail in doomdef.h

Author: tseng0201

src/doomdef.h

@@ -29,10 +29,19 @@
 
 // Disable screens wipe effect, you will get worse game experience, 
 // but it can save about 130KB on DOOMHEAP.
+// In f_wipe.c, only wipe_initMelt() and wipe_shittyColMajorXform() call Z_Malloc ask for some sapce,
+// wipe_initMelt() ask 320 * 8(width * sizeof(int)) = 2560 bytes,
+// wipe_shittyColMajorXform() ask 160 * 200 * 2(width/2 * height*2) = 64000 bytes,
+// it will be call twice so it will totaly ask 128000 bytes,
+// it means we can save 2560 + 128000 = 130560 bytes on DOOMHEAP when disable screens wipe.
 #define DISABLE_WIPES
 
 // Discard screen buffers, any screen effect will direct output on your screen, 
-// It can save 192kb on heap. 
+// It can save 192kb memory usage.
+// Each screen buffer is 320 * 200 * 1 = 64000 bytes, 
+// COMBINE_SCREENS will make four screen buffers merge to one,
+// so we can save (4 - 1) * 320 * 200 = 192000 bytes.
+// In this Implement it will set "CombinedScreens[SCREENWIDTH*SCREENHEIGHT]" to replace original "CombinedScreens[SCREENWIDTH*SCREENHEIGHT*4]".
 // Remeber you can only use this when disable screens wipe.
 #define COMBINE_SCREENS