[gentoo-sparc] sparc64 bit profiles for review

I can safely say i have been running these in production with a native 
64bit userland and 32 bit multilib for over 6 months now. My changes can 
be found here.

https://github.com/5YN3R6Y/gentoo

I'm open to review on these changes, but it should keep compatibility 
with the old profiles. Feel free to attempt to build stage3's from this, 
but building a sparc64 stage3 will be tough on the current profiles. I 
will upload some of my own stage3's soon and link them here for testing 
purposes.