[3.3/mainline] Add 64bit SSE intrincisc

[Jan Hubicka]

> What about documenting these builtins ?
Hmm, the intrincisc themselves are documented by AMD.
The builtins, I think, should be considered internal, as we've changed
these several times so they are definitly not something we want to be
backward compatible with.

There is documentation, but it is out of date for other builtins too.
Perhaps I can make separate pass trought and document them, or
altenrativly wipe out the existing bits and add reference to official
sources?

Honza
> 
> -- 
> Sylvain