ECPG: Split ecpg_do() further up and introduce ecpg_do_prologue().
      Add an error path to return if ecpg_strdup(setlocale()) fails.
ECPG: Move PGresult *results into struct statement from ecpg_execute().
ECPG: Split ecpg_execute() up into 4 pieces: ecpg_build_params(),
      ecpg_autostart_transaction(), a smaller ecpg_execute() and
      ecpg_process_output().