Fix unicode support in db(1).
command() receives a char* that is assigned to lp, which is a Rune*,
and lp is incremented later in readchar(), so each read consumed 4 bytes.
The only time command() is called is in runpcs() with bkpt->comm,
which is a char* built in subpcs through a char*, so the string stored in
bkpt->comm was not a Rune string. A way to test the bug is:

db program
main:b argv/X
:r


Reference: /n/sources/patch/unicode-db
Date: Thu Mar 19 07:23:13 CET 2015
Signed-off-by: k0ga@shike2.com

--- /sys/src/cmd/db/command.c	Thu Mar 19 07:06:13 2015
+++ /sys/src/cmd/db/command.c	Thu Mar 19 07:06:09 2015
@@ -24,7 +24,7 @@
 
 /* command decoding */
 
-command(char *buf, int defcom)
+command(Rune *buf, int defcom)
 {
 	char	*reg;
 	char	savc;
@@ -39,7 +39,7 @@
 		if (*buf==EOR)
 			return(FALSE);
 		clrinp();
-		lp=(Rune*)buf;
+		lp=buf;
 	}
 	do {
 		adrflg=expr(0);		/* first address */
--- /sys/src/cmd/db/defs.h	Thu Mar 19 07:06:19 2015
+++ /sys/src/cmd/db/defs.h	Thu Mar 19 07:06:16 2015
@@ -64,7 +64,7 @@
 	int	count;
 	int	initcnt;
 	int	flag;
-	char	comm[MAXCOM];
+	Rune	comm[MAXCOM];
 	BKPT	*nxtbkpt;
 };
 
--- /sys/src/cmd/db/fns.h	Thu Mar 19 07:06:26 2015
+++ /sys/src/cmd/db/fns.h	Thu Mar 19 07:06:22 2015
@@ -8,7 +8,7 @@
 void		cmdmap(Map*);
 void		cmdsrc(int, Map*);
 void		cmdwrite(int, Map*);
-int		command(char*, int);
+int		command(Rune*, int);
 int		convdig(int);
 void		ctrace(int);
 WORD		defval(WORD);
--- /sys/src/cmd/db/pcs.c	Thu Mar 19 07:06:32 2015
+++ /sys/src/cmd/db/pcs.c	Thu Mar 19 07:06:28 2015
@@ -20,7 +20,7 @@
 	int	n, r;
 	long line, curr;
 	BKPT *bk;
-	char *comptr;
+	Rune *comptr;
 
 	runmode=SINGLE;
 	r = 0;
--- /sys/src/cmd/db/print.c	Thu Mar 19 07:06:39 2015
+++ /sys/src/cmd/db/print.c	Thu Mar 19 07:06:35 2015
@@ -166,7 +166,7 @@
 				dprint(buf);
 				if (bk->count != 1)
 					dprint(",%d", bk->count);
-				dprint(":%c %s", bk->flag == BKPTTMP ? 'B' : 'b', bk->comm);
+				dprint(":%c %S", bk->flag == BKPTTMP ? 'B' : 'b', bk->comm);
 			}
 		break;