Implement bitwise SSE ops & _mm_cmp*_ss (rust-lang#103)

* Add _mm_{and,andnot,or,xor}_ps

* Add _mm_cmpeq_ss

* Add _mm_cmplt_ss

* Add _mm_cmple_ss

* Add _mm_cmpgt_ss

* Add _mm_cmpge_ss

* Add _mm_cmpneq_ss

* Add _mm_cmpnlt_ss

* Add _mm_cmpnle_ss

* Add _mm_cmpngt_ss

* Add _mm_cmpnge_ss

* Add _mm_cmpord_ss

* Add _mm_cmpunord_ss

* Fix _mm_{and,andnot,or,xor}_ps tests for i586

LLVM for i586 doesn't seem to generate `andps`, and instead generates 4
`and`s. Similar for the other operations.