This change
This change

  <http://cvs.sourceforge.net/viewcvs.py/monetdb/MonetDB/src/mapi/clients/C/Mapi.mx?r1=1.166&r2=1.167>

caused a test failure:

  t\75mil......ok 14/30
  #     Failed test (t\75mil.t at line 58)
  #                   '-4'
  #     doesn't match '(?-xism:!ERROR:)'

(Before, mapi_error() returned 0.)
Now, we always call mapi_result_error().

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb