double-buffering added using pixmap (finally).

results in a lot of simplification :
	- no more dirty flags (perf are good enough).
	- no more ugly gfx call in emulation functions.
LINESPACE removed from config.h.
BORDER is now handled correctly.

config.h

@@ -3,8 +3,7 @@
 
 #define FONT "6x13"
 #define BOLDFONT FONT"bold"
-#define BORDER 3
-#define LINESPACE 0 /* additional pixel between each line */
+#define BORDER 2
 
 /* Terminal colors */
 static const char *colorname[] = {