Don't add service name to read config file segments if it's "MySQL"
Fixed possible memory leak when CHANGE USER failed.


include/mysql_com.h:
  Change back service name to MySQL (With new, better spelling)
myisam/myisamchk.c:
  Improved --help
sql/mysqld.cc:
  Don't add service name to read config file segments if it's "MySQL"
sql/sql_parse.cc:
  Fixed possible memory leak when CHANGE USER failed.