The patch.txt shows the changes you need to make to the files. Replace the lines shown with a - by the lines shown with a +. The files that need to be edited are model/cartesian_grid/pvd_mod.f and model/des/vtp_mod.f. You should not attempt to compile the patch file as is.
Basically you need to add the ACTION='READWRITE' descriptor to the open statements in the above two files.
If you still struggle with this we will attach the entire files.