doc: renamed the "errno" return value to "errcode" for consistency.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: sjnam

README.markdown

@@ -79,14 +79,14 @@ Synopsis
 
                 -- or connect to a unix domain socket file listened
                 -- by a mysql server:
-                --     local ok, err, errno, sqlstate =
+                --     local ok, err, errcode, sqlstate =
                 --           db:connect{
                 --              path = "/path/to/mysql.sock",
                 --              database = "ngx_test",
                 --              user = "ngx_test",
                 --              password = "ngx_test" }
 
-                local ok, err, errno, sqlstate = db:connect{
+                local ok, err, errcode, sqlstate = db:connect{
                     host = "127.0.0.1",
                     port = 3306,
                     database = "ngx_test",
@@ -95,35 +95,35 @@ Synopsis
                     max_packet_size = 1024 * 1024 }
 
                 if not ok then
-                    ngx.say("failed to connect: ", err, ": ", errno, " ", sqlstate)
+                    ngx.say("failed to connect: ", err, ": ", errcode, " ", sqlstate)
                     return
                 end
 
                 ngx.say("connected to mysql.")
 
-                local res, err, errno, sqlstate =
+                local res, err, errcode, sqlstate =
                     db:query("drop table if exists cats")
                 if not res then
-                    ngx.say("bad result: ", err, ": ", errno, ": ", sqlstate, ".")
+                    ngx.say("bad result: ", err, ": ", errcode, ": ", sqlstate, ".")
                     return
                 end
 
-                res, err, errno, sqlstate =
+                res, err, errcode, sqlstate =
                     db:query("create table cats "
                              .. "(id serial primary key, "
                              .. "name varchar(5))")
                 if not res then
-                    ngx.say("bad result: ", err, ": ", errno, ": ", sqlstate, ".")
+                    ngx.say("bad result: ", err, ": ", errcode, ": ", sqlstate, ".")
                     return
                 end
 
                 ngx.say("table cats created.")
 
-                res, err, errno, sqlstate =
+                res, err, errcode, sqlstate =
                     db:query("insert into cats (name) "
                              .. "values (\'Bob\'),(\'\'),(null)")
                 if not res then
-                    ngx.say("bad result: ", err, ": ", errno, ": ", sqlstate, ".")
+                    ngx.say("bad result: ", err, ": ", errcode, ": ", sqlstate, ".")
                     return
                 end
 
@@ -132,10 +132,10 @@ Synopsis
 
                 -- run a select query, expected about 10 rows in
                 -- the result set:
-                res, err, errno, sqlstate =
+                res, err, errcode, sqlstate =
                     db:query("select * from cats order by id asc", 10)
                 if not res then
-                    ngx.say("bad result: ", err, ": ", errno, ": ", sqlstate, ".")
+                    ngx.say("bad result: ", err, ": ", errcode, ": ", sqlstate, ".")
                     return
                 end
 
@@ -284,9 +284,9 @@ You should use the [read_result](#read_result) method to read the MySQL replies
 
 read_result
 -----------
-`syntax: res, err, errno, sqlstate = db:read_result()`
+`syntax: res, err, errcode, sqlstate = db:read_result()`
 
-`syntax: res, err, errno, sqlstate = db:read_result(nrows)`
+`syntax: res, err, errcode, sqlstate = db:read_result(nrows)`
 
 Reads in one result returned from the MySQL server.
 
@@ -381,31 +381,31 @@ Below is a trivial example for this:
     local mysql = require "resty.mysql"
 
     local db = mysql:new()
-    local ok, err, errno, sqlstate = db:connect({
+    local ok, err, errcode, sqlstate = db:connect({
         host = "127.0.0.1",
         port = 3306,
         database = "world",
         user = "monty",
         password = "pass"})
 
     if not ok then
-        ngx.log(ngx.ERR, "failed to connect: ", err, ": ", errno, " ", sqlstate)
+        ngx.log(ngx.ERR, "failed to connect: ", err, ": ", errcode, " ", sqlstate)
         return ngx.exit(500)
     end
 
-    res, err, errno, sqlstate = db:query("select 1; select 2; select 3;")
+    res, err, errcode, sqlstate = db:query("select 1; select 2; select 3;")
     if not res then
-        ngx.log(ngx.ERR, "bad result #1: ", err, ": ", errno, ": ", sqlstate, ".")
+        ngx.log(ngx.ERR, "bad result #1: ", err, ": ", errcode, ": ", sqlstate, ".")
         return ngx.exit(500)
     end
 
     ngx.say("result #1: ", cjson.encode(res))
 
     local i = 2
     while err == "again" do
-        res, err, errno, sqlstate = db:read_result()
+        res, err, errcode, sqlstate = db:read_result()
         if not res then
-            ngx.log(ngx.ERR, "bad result #", i, ": ", err, ": ", errno, ": ", sqlstate, ".")
+            ngx.log(ngx.ERR, "bad result #", i, ": ", err, ": ", errcode, ": ", sqlstate, ".")
             return ngx.exit(500)
         end