acid \B format prints 1 garbage character after fmt
e.g.:
acid: 0xe\B
0b00000000000000000000000000001110p

fix by using %b format (which itself needed
a fix to print 0b as prefix if FmtSharp is set).

a clean comple requires this addition to libc.h:

/n/sources/plan9//sys/include/libc.h:177,184 - libc.h:180,189
  
  #pragma	varargck	type	"lld"	vlong
  #pragma	varargck	type	"llx"	vlong
+ #pragma	varargck	type	"llb"	vlong
  #pragma	varargck	type	"lld"	uvlong
  #pragma	varargck	type	"llx"	uvlong
+ #pragma	varargck	type	"llb"	uvlong
  #pragma	varargck	type	"ld"	long
  #pragma	varargck	type	"lx"	long
  #pragma	varargck	type	"lb"	long

Notes:
Fri Jul 29 16:48:39 EDT 2011 geoff
    fixing the actual dofmt bug has also fixed acid.
    a decision about %#b emitting 0b has been deferred.


Reference: /n/sources/patch/maybe/acidbfmt
Date: Sun Sep 12 20:10:30 CES 2010
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/libc/fmt/dofmt.c	Sun Sep 12 20:05:09 2010
+++ /sys/src/libc/fmt/dofmt.c	Sun Sep 12 20:05:08 2010
@@ -415,12 +415,17 @@
 		*p-- = '0';
 		n = 1;
 	}
-	for(w = f->prec; n < w && p > buf+3; n++)
+	for(w = f->prec; n < w && p > buf+4; n++){
+		if((fl & FmtComma) && n % 4 == 3){
+			*p-- = ',';
+			n++;
+		}
 		*p-- = '0';
+	}
 	if(neg || (fl & (FmtSign|FmtSpace)))
 		n++;
 	if(fl & FmtSharp){
-		if(base == 16)
+		if(base == 16 || base == 2)
 			n += 2;
 		else if(base == 8){
 			if(p[1] == '0')
@@ -430,14 +435,19 @@
 		}
 	}
 	if((fl & FmtZero) && !(fl & (FmtLeft|FmtPrec))){
-		for(w = f->width; n < w && p > buf+3; n++)
+		for(w = f->width; n < w && p > buf+4; n++){
+			if((fl & FmtComma) && n % 4 == 3){
+				*p-- = ',';
+				n++;
+			}
 			*p-- = '0';
+		}
 		f->width = 0;
 	}
 	if(fl & FmtSharp){
-		if(base == 16)
+		if(base == 16 || base == 2)
 			*p-- = f->r;
-		if(base == 16 || base == 8)
+		if(base == 16 || base == 8 || base == 2)
 			*p-- = '0';
 	}
 	if(neg)
@@ -512,12 +522,13 @@
 int
 _badfmt(Fmt *f)
 {
-	char x[3];
+	char x[2+UTFmax];
+	int n;
 
 	x[0] = '%';
-	x[1] = f->r;
-	x[2] = '%';
-	f->prec = 3;
-	_fmtcpy(f, x, 3, 3);
+	n = 1 + runetochar(x+1, (Rune*)&f->r);
+	x[n++] = '%';
+	f->prec = n;
+	_fmtcpy(f, x, n, n);
 	return 0;
 }
--- /sys/src/cmd/acid/builtin.c	Sun Sep 12 20:05:18 2010
+++ /sys/src/cmd/acid/builtin.c	Sun Sep 12 20:05:15 2010
@@ -969,7 +969,6 @@
 void
 patom(char type, Store *res)
 {
-	int i;
 	char buf[512];
 	extern char *typenames[];
 
@@ -987,14 +986,7 @@
 		Bprint(bout, "%C", (int)res->ival);
 		break;
 	case 'B':
-		memset(buf, '0', 34);
-		buf[1] = 'b';
-		for(i = 0; i < 32; i++) {
-			if(res->ival & (1<<i))
-				buf[33-i] = '1';
-		}
-		buf[35] = '\0';
-		Bprint(bout, "%s", buf);
+		Bprint(bout, "%#.32llub", res->ival);
 		break;
 	case 'b':
 		Bprint(bout, "%.2x", (int)res->ival&0xff);