Return error from WriteByte, to match bufio.Writer.

R=gri
DELTA=4  (1 added, 0 deleted, 3 changed)
OCL=28868
CL=28899

src/lib/io/bytebuffer.go

@@ -75,10 +75,11 @@ func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
 }
 
 // WriteByte appends the byte c to the buffer.
-// Because Write never fails and WriteByte is not part of the
-// io.Writer interface, it does not need to return a value.
-func (b *ByteBuffer) WriteByte(c byte) {
+// The returned error is always nil, but is included
+// to match bufio.Writer's WriteByte.
+func (b *ByteBuffer) WriteByte(c byte) os.Error {
 	b.Write([]byte{c});
+	return nil;
 }
 
 // Read reads the next len(p) bytes from the buffer or until the buffer