Fixed memory leak printing when doing 'mysqld --version', 'mysqld --debug --help' and 'mysqld --debug --help --verbose'


mysys/my_init.c:
  Moved checking if we should call DBUG_END() before my_thread_end() as otherwise we will not free DBUG variables and files.
mysys/thr_lock.c:
  Fixed compiler warning
sql/mysqld.cc:
  Fixed memory leaks when using mysqld --help and mysqld --version
  Added --debug as an option that works for all builds. For non debug builds we now get a warning.
strings/dtoa.c:
  Fixed valgrind warning (c could contain data outside of the given string)