[toplevel] remove empty cases

[Joseph S. Myers]

On Thu, 24 Mar 2011, Paolo Bonzini wrote:

> This enables omit-frame-pointer for i386-solaris.  I honestly haven't
> bootstrapped it, but I don't expect any problems (and if they appear, it's
> much better to fix them ;).

How about killing mh-x86omitfp?  The x86 compiler defaults to 
-fomit-frame-pointer on most platforms now anyway.

-- 
Joseph S. Myers
joseph@codesourcery.com