Fixed typos

- Removed duplicate words, like "the the" and "to to"
- Removed duplicate lines (one double sort line found in mysql.cc)
- Fixed some typos found while searching for duplicate words.

Command used to find duplicate words:
egrep -rI "\s([a-zA-Z]+)\s+\1\s" | grep -v param

Thanks to Artjoms Rimdjonoks for the command and pointing out the
spelling errors.

sql/sql_table.cc

@@ -4478,7 +4478,7 @@ handler *mysql_create_frm_image(THD *thd, HA_CREATE_INFO *create_info,
   /*
     Unless table's storage engine supports partitioning natively
     don't allow foreign keys on partitioned tables (they won't
-    work work even with InnoDB beneath of partitioning engine).
+    work even with InnoDB beneath of partitioning engine).
     If storage engine handles partitioning natively (like NDB)
     foreign keys support is possible, so we let the engine decide.
   */
@@ -11722,7 +11722,7 @@ do_continue:;
     5) Write statement to the binary log.
     6) If we are under LOCK TABLES and do ALTER TABLE ... RENAME we
        remove placeholders and release metadata locks.
-    7) If we are not not under LOCK TABLES we rely on the caller
+    7) If we are not under LOCK TABLES we rely on the caller
       (mysql_execute_command()) to release metadata locks.
   */