Returns the column number associated with the column name

Property definitions

postgresql $ NativePGResult :: fnumber
  # Returns the column number associated with the column name
  fun fnumber(column_name:String):Int import String.to_cstring `{
    return PQfnumber(self, String_to_cstring(column_name));
  `}
lib/postgresql/native_postgres.nit:70,3--73,4