correct the bursting.  see the 9fans discussion.  we can't combine
classes if the first byte is different.

Reference: /n/atom/patch/applied/grepburst
Date: Sun Mar 30 20:13:43 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/grep/comp.c	Sun Mar 30 20:12:56 2014
+++ /sys/src/cmd/grep/comp.c	Sun Mar 30 20:12:57 2014
@@ -141,7 +141,7 @@
 {
 	0x003f,
 	0x0fff,
-	0xffff,
+	0x03ffff,
 };
 
 Re2
@@ -277,7 +277,7 @@
 			x = re2or(x, rclass(ov, p[0]-1));
 			ov = p[1]+1;
 		}
-		x = re2or(x, rclass(ov, 0xffff));
+		x = re2or(x, rclass(ov, Runemax));
 	} else {
 		x = rclass(p[0], p[1]);
 		for(p+=2; *p; p+=2)