Aim: Returns sum of offsets through mask.
The routine declaration is:
integer function inMask(offX, offY, patabove)
! offX, offY: local column and row offsets
! patabove : 1 means count, 0 means ignore (like output of getpixelInE2)
integer, dimension(-1:1), intent(in) :: offX, offY
integer(kind=int16), dimension(-1:1,-1:1), intent(in) :: patabove