Add a new option: -hcsuf <suffix> which renames the .hc suffix to
<suffix> for this compilation, in the same way as -osuf and -hisuf.

To even things up, remove partial support for '-ohi -', which
allegedly dumped the .hi file to stdout but in reality never worked.
It's a strange thing to want to do anyway, but in any case you could
always say '-ohi /dev/stdout', or even 'ghc Foo.hs && cat Foo.hi'.