core.simd woes

[jerro]

> An alternative approach is to have one module per architecture 
> or compiler.

You mean like something like std.simd.x86_gdc? In this case a 
user would need to write a different version of his code for each 
compiler or write his own  wrappers (which is basically what we 
have now). This could cause a lot of redundant work. What is 
worse, some people wouldn't bother, and then we would have code 
that only works with one D compiler.