Added buf_swrite.

misc/iobuf.h

@@ -13,4 +13,6 @@ int buf_grow(struct io_buffer *iob, size_t size);
 int buf_write(struct io_buffer *iob, const void *data, size_t size);
 int buf_print(struct io_buffer *iob, const char *fmt, ...);
 
+#define buf_swrite(iob, s) buf_write(iob, s, sizeof(s) - 1)
+
 #endif