mx --J & Cie.

[Gilles Duboscq]

Hello,

While cleaning some thing up in mx & mx_graal I noticed some strange
behaviour around the following options:
  --J @<args>           Java VM arguments (e.g. --J @-dsa)
  --Jp @<args>          prefix Java VM arguments (e.g. --Jp @-dsa)
  --Ja @<args>          suffix Java VM arguments (e.g. --Ja @-dsa)

For example these options are not used when using mx vm.

These options don't seem to be used anyway so I'd propose to remove
them altogether. Is this a problem for anyone?

-Gilles