SSE converison patterns

[Jan Hubicka]

> Surely the dest should be register_operand.
> No constraints in define_expand.  Also missing the predicate
> to disable this pattern.  I.e.  "TARGET_80387 || TARGET_SSE2".
Both fixed - thanks for noticing.  I've also fixed constraints and
operands of extendsfdf2. Originally I've had some confussion about
where memory operand is allowed and I see, I didn't fixed everything
properly.

Just running bootstrap/make check to install it.

Thanks,
Honza
> 
> Otherwise ok.
> 
> 
> r~