PATCH for invoke.texi MIPS switches

[Jim Wilson]

Please do not document the -mabi=o32 and -mabi=n64 options because they do
not work, and they probably never will.  They were added by Kenner, without
consulting with me, and they have never worked right.  It would be better to
delete them; I just never got around to it.  If you want to submit a patch
that deletes them, that would be great.

In general, having multiple names for the same option is a bad idea, because
there is no easy way to write specs that correctly handle all of the names.
This is the problem with -mabi=o32 and -mabi=n64: none of the specs handle
them correctly.  For instance, if you use -mabi=n64, size_t will be wrong.

Otherwise, the patch is OK.

Jim