nghttp: Allow multiple -v option to increase verbosity

Now the number of -v option specifies verbosity level.  Current all
verbose output are turned on for at lest one -v option, except for the
debug output for each data chunk which is only turned on more than one
-v options.

src/nghttp.cc

@@ -95,9 +95,9 @@ struct Config {
   int timeout;
   int window_bits;
   int connection_window_bits;
+  int verbose;
   bool null_out;
   bool remote_name;
-  bool verbose;
   bool get_assets;
   bool stat;
   bool upgrade;
@@ -114,9 +114,9 @@ struct Config {
       timeout(-1),
       window_bits(-1),
       connection_window_bits(-1),
+      verbose(0),
       null_out(false),
       remote_name(false),
-      verbose(false),
       get_assets(false),
       stat(false),
       upgrade(false),
@@ -1129,7 +1129,7 @@ int on_data_chunk_recv_callback
     return 0;
   }
 
-  if(config.verbose) {
+  if(config.verbose >= 2) {
     verbose_on_data_chunk_recv_callback(session, flags, stream_id, data, len,
                                         user_data);
   }
@@ -1945,6 +1945,8 @@ void print_help(std::ostream& out)
 Options:
   -v, --verbose      Print  debug information  such  as reception  and
                      transmission  of  frames  and  name/value  pairs.
+                     Specifying this  option multiple  times increases
+                     verbosity.
   -n, --null-out     Discard downloaded data.
   -O, --remote-name  Save download data in the current directory.  The
                      filename is dereived from  URI.  If URI ends with
@@ -2077,7 +2079,7 @@ int main(int argc, char **argv)
       break;
     }
     case 'v':
-      config.verbose = true;
+      ++config.verbose;
       break;
     case 't':
       config.timeout = atoi(optarg) * 1000;