[FLASH-BUGS] 3 flash2.1 bugs

[Tomasz Plewa]

Dear Erik-Jan:

Thank you for your report.

I will address the first point: 

> Hard coded value in source/mesh/amr/paramesh2.0/ref_marking.F90:

The best and permanent fix is to remove the constant and check for
denom being non-zero.

! compute the error
                 num = 0.
                 denom = 0.

                 do kk = 1, ndim2
                    num = num + delu2(kk)**2
                    denom = denom + (delu3(kk) + &
                         &                       epsil*delu4(kk))**2
                 end do

! mz -- compare the square of the error

                 if ( denom > 0. ) then
                    error(lb) = max(error(lb),num/denom)
                 else
                    error(lb) = 0.
                 endif

Hope this helps.

Best wishes,
Tomek
--