Cleaned up charset.c
Removed non fatal memory leak in charset.c


include/my_sys.h:
  Enchanced my_once..() functions.
mysys/charset.c:
  Moved my_once_strdup() to my_once.cc
  Added usage of my_once_memdup()
  A lot of indentation changes.
mysys/my_once.c:
  Enchanced my_once..() functions.