separate boot partition support

[OKUJI Yoshinori]

  Because many people make mistakes about their separate boot
partitions, I have added the support into the command "setup" and the
utility "grub-install". The command "setup" now also supports
`--prefix', so that you can specify a directory but
"/boot/grub". Please test these new features. If there is no problem,
I'll add a tag, prepare_0_5_96, into the CVS, even though there are
some pending tasks, because I don't want to delay next test release
any longer.

  But there is one thing which must be done soon: Update the docs. In
particular, we should write a chapter about the serial terminal
support. Alessandro, would you like to work on that?

Okuji