Problem was that we checked for existing connection in stmt_close
and did not free(stmt) if it's closed (that didn't work well with
embedded)
I just added new flag to the stmt_close and now we check it instead
of connection


libmysql/client_settings.h:
  declaration changed
libmysql/libmysql.c:
  stmt_close and it's calls modified
sql-common/client.c:
  stmt_close call modified