Don't use section-relative GOT relocations for MIPS VxWorks

[Richard Sandiford]

Eric Christopher <echristo@apple.com> writes:
>> Tested on mips-wrs-vxworks.  OK to install?
>
> Sure, though if you could change the 0 to a define that makes reading  
> a bit easier?

OK, I changed the 0 to STN_UNDEF and checked it in.

Thanks,
Richard