More Front End Vector Support

[Iain Buclaw]

Morning,

I've noticed that 256bit vector support has been added to the D 
frontend during the development stages of 2.060 whilst was 
looking around in druntime core.

https://github.com/D-Programming-Language/druntime/commit/fcc91588e89fa48b699f0efe0cdfb8c23e2bb4ae


Is anyone willing to object if I raise a pull request to add 
64bit Vector support in the D frontend too for architectures that 
support? This includes i386/x86_64 using MMX extensions, and ARM 
using NEON extensions.

Not sure how well DMD would cope with the type in it's backend 
though, but can always reject it in its backend with an error.


Regards
Iain