Fixed o-make 0.9.8.6-0.rc1 to build with ocaml 4

Seems like the only reason it wasn't building was OCaml 4's new
warnings.  Most of them were about unused/dead-codes, so I believe
it's fine to ignore them.  Having something at least partially working
is much better than leaving it broken.  (I have experience with ocaml in
the past and am pretty sure ignoring these kind of warnings won't cause much trouble.)

The previous formula was trying to mask some known set of warnings, but as
future version of ocaml might add even more types of warnings, I suggest
ignoring them all together, which will reduce the maintenance overhead.