prevent garbage being printed; for example:

	; 8.out fubar
	<stdin>:1: (error) 8.out: can't open fubar: 'fubar' directory entry not found

	/sys/lib/acid/port
	/sys/lib/acid/386
	no symbol information
	acid: new()
	8.out: <stdin>:2 (fatal problem) new: exec ��: 'fubar' directory entry not found
	<stdin>:2: (error) msg: pid=5369 waitstop: process exited

Reference: /n/sources/patch/maybe/acid-nits
Date: Sun Sep  4 16:59:36 CES 2011
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/acid/acid.h	Sun Sep  4 16:57:40 2011
+++ /sys/src/cmd/acid/acid.h	Sun Sep  4 16:57:38 2011
@@ -244,6 +244,10 @@
 int	yylex(void);
 int	yyparse(void);
 
+#pragma	varargck	argpos	error		1
+#pragma	varargck	argpos	fatal		1
+#pragma	varargck	argpos	yyerror		1
+
 enum
 {
 	ONAME,
--- /sys/src/cmd/acid/expr.c	Sun Sep  4 16:57:43 2011
+++ /sys/src/cmd/acid/expr.c	Sun Sep  4 16:57:41 2011
@@ -537,7 +537,7 @@
 	res->op = OCONST;
 	res->type = TINT;
 	if(l.type != TINT || r.type != TINT)
-		error("bad expr type %");
+		error("bad expr type %%");
 	res->ival = l.ival%r.ival;
 }
 
--- /sys/src/cmd/acid/proc.c	Sun Sep  4 16:57:45 2011
+++ /sys/src/cmd/acid/proc.c	Sun Sep  4 16:57:44 2011
@@ -87,7 +87,7 @@
 		open("/dev/cons", OWRITE);
 		open("/dev/cons", OWRITE);
 		exec(argv[0], argv);
-		fatal("new: exec %s: %r");
+		fatal("new: exec %s: %r", argv[0]);
 	default:
 		install(pid);
 		msg(pid, "waitstop");