Fix for LPBug#520243: useability bug of thread pool configuration

Now mysqld --help --verbose shows the value for thread-handling
Fixed also that mysqld --one-thread works as expected.

sql/mysqld.cc

@@ -598,6 +598,7 @@ char *mysqld_unix_port, *opt_mysql_tmpdir;
 const char **errmesg;			/**< Error messages */
 const char *myisam_recover_options_str="OFF";
 const char *myisam_stats_method_str="nulls_unequal";
+const char *opt_thread_handling= thread_handling_typelib.type_names[0];
 
 /** name of reference on left espression in rewritten IN subquery */
 const char *in_left_expr_name= "<left expr>";
@@ -7290,7 +7291,8 @@ The minimum value for this variable is 4096.",
    1024, 0},
   {"thread_handling", OPT_THREAD_HANDLING,
    "Define threads usage for handling queries:  "
-   "one-thread-per-connection or no-threads", 0, 0,
+   "one-thread-per-connection or no-threads",
+   (uchar**) &opt_thread_handling, (uchar**) &opt_thread_handling,
    0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"updatable_views_with_limit", OPT_UPDATABLE_VIEWS_WITH_LIMIT,
    "1 = YES = Don't issue an error message (warning only) if a VIEW without presence of a key of the underlying table is used in queries with a LIMIT clause for updating. 0 = NO = Prohibit update of a VIEW, which does not contain a key of the underlying table and the query uses a LIMIT clause (usually get from GUI tools).",
@@ -8721,14 +8723,15 @@ mysqld_get_one_option(int optid,
     break;
   }
   case OPT_ONE_THREAD:
-    global_system_variables.thread_handling=
-      SCHEDULER_ONE_THREAD_PER_CONNECTION;
+    global_system_variables.thread_handling= SCHEDULER_NO_THREADS;
+    opt_thread_handling= thread_handling_typelib.type_names[global_system_variables.thread_handling];
     break;
   case OPT_THREAD_HANDLING:
   {
     int id;
     if (!find_opt_type(argument, &thread_handling_typelib, opt->name, &id))
       global_system_variables.thread_handling= id - 1;
+    opt_thread_handling= thread_handling_typelib.type_names[global_system_variables.thread_handling];
     break;
   }
   case OPT_FT_BOOLEAN_SYNTAX: