First set of fixes

My very first pull request... 

The thing does not yet compile under linux, but I'm making strides towards it. 
What is missing are the operator[] in float8_sse and float16_sse
Same on linux. The problem is, depending on the configuration available where you're compiling, you have to include the apropriate header. On linux at least, you get a compiler error if you include immintrin.h without specifying -mavx. That's why such an ifdef hackery is required