a few missing headers and minor fixes

fix corking behavior for the case where a buffer follows a buffer in
iob_send

io/io_debugstring.c

@@ -1,7 +1,7 @@
 #include "io_internal.h"
 #include <iarray.h>
 #include <fmt.h>
-#include <time.h>
+#include <sys/time.h>
 
 unsigned int io_debugstring(int64 s,char* buf,unsigned int bufsize) {
   struct timeval tv;