brown paper bag patch.  mem.h was forgotten in previous patch
to add sys to pc port

Reference: /n/atom/patch/applied2013/fspcmachsz
Date: Tue Aug 27 18:32:32 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/fs/pc/mem.h	Tue Aug 27 18:31:55 2013
+++ /sys/src/fs/pc/mem.h	Tue Aug 27 18:31:56 2013
@@ -1,15 +1,25 @@
+#define KiB		1024u			/* Kibi 0x0000000000000400 */
+#define MiB		1048576u		/* Mebi 0x0000000000100000 */
+#define GiB		1073741824u		/* Gibi 000000000040000000 */
+#define TiB		1099511627776ull	/* Tebi 0x0000010000000000 */
+#define PiB		1125899906842624ull	/* Pebi 0x0004000000000000 */
+#define EiB		1152921504606846976ull	/* Exbi 0x1000000000000000 */
+
 #define	BY2WD		4			/* bytes per word */
 #define BY2V		8			/* bytes per vlong */
 #define	BY2PG		4096			/* bytes per page */
 #define	PGSHIFT		12			/* log(BY2PG) */
 #define PGROUND(s)	(((s)+(BY2PG-1))&~(BY2PG-1))
 #define MB		(1024*1024)
-#define MiB		(1024*1024)
 
 #define	HZ		1000			/* clock frequency */
 #define	TK2MS(t)	(((ulong)(t)*1000)/HZ)	/* ticks to milliseconds - beware rounding */
 #define	MS2TK(t)	(((ulong)(t)*HZ)/1000)	/* milliseconds to ticks - beware rounding */
 #define	TK2SEC(t)	((t)/HZ)		/* ticks to seconds */
+
+#define	MACHSZ	(4*KiB)
+#define	MACHMAX	32
+#define	MACHSTKSZ	(6*4*KiB)
 
 /*
  * Fundamental addresses