libmysql/libmysql.c:
  Rename.
libmysqld/lib_sql.cc:
  Rename.
sql/item_cmpfunc.cc:
  Use proper method to check for stmt prepare, only_prepare is removed.
sql/mysql_priv.h:
  Remove an obsolete define. Rename mysql_stmt_free to mysql_stmt_close.
sql/sql_class.h:
  Remove THD::only_prepare.
  Rename.
sql/sql_lex.cc:
  Rename COM_PREPARE -> COM_STMT_PREPARE
sql/sql_parse.cc:
  Rename.
sql/sql_prepare.cc:
  Rename.
sql/sql_yacc.yy:
  Rename.
tests/mysql_client_test.c:
  Rename.