Add write support for Fgdb layers and make it possible to remove a prefix from the expressions. The expressions returned by arcgis for Fgdb data contain the data source name as a prefix. Mapserver does not need it and does not match those expressions so they have to be removed

SYMBOL 
  NAME "l_markerline_18pt_0-0-0_raute"
  TYPE VECTOR
  POINTS
    0 0.5
    0.5 0
    1 0.5
    0.5 1
    0 0.5
  END
  FILLED FALSE 
END