MEDIUM: stats: report per-backend and per-server time stats in HTML and CSV outputs

The time statistics computed by previous patches are now reported in the
HTML stats in the tips related to the total sessions for backend and servers,
and as separate columns for the CSV stats.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 36a19b8..51798b4 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -13011,6 +13011,10 @@
  55. lastsess: number of seconds since last session assigned to server/backend
  56. last_chk: last health check contents or textual error
  57. last_agt: last agent check contents or textual error
+ 58. qtime: the average queue time in ms over the 1024 last requests
+ 59. ctime: the average connect time in ms over the 1024 last requests
+ 60. rtime: the average response time in ms over the 1024 last requests (0 for TCP)
+ 61. ttime: the average total session time in ms over the 1024 last requests
 
 
 9.2. Unix Socket commands