Add support for Fortran LOGICAL type

I understand that SQLite3 does not have a separate boolean datatype but allows the declaration of columns with boolean type and stores these as integers (1 or 0). I have a Fortran application where I would like to read booleans out of an sqlite table directly into a Fortran LOGICAL type variable. To support this in a clean way that dosen't involve intrinsic conversion from INTEGER to LOGICAL (although this is supported by gfortran), I would like to propose adding the following function to sqliteff.f90:

    function sqliteff_column_bool(statement, col) result(val)
        type(SqliteStatement_t), intent(inout) :: statement
        integer, intent(in) :: col
        integer :: ival
        logical :: val

        interface
            function csqlite3_column_int( &
                    handle, &
                    col) &
                    result(val) &
                    bind(C, name = "csqlite3_column_int")
                import c_int, c_ptr
                type(c_ptr), intent(inout) :: handle
                integer(kind=c_int), value, intent(in) :: col
                integer(kind=c_int) :: ival
            end function csqlite3_column_int
        end interface
        
        ival = csqlite3_column_int(statement%handle, col)
        
        if (ival == 0) then
          val = .false.
        else
          val = .true.
        end if
        
    end function sqliteff_column_bool

I have implemented and tested the function in my own installation and it works as expected.

Thanks for developing this very useful package!