OpenMP support

[Iain Buclaw]

== Quote from Scorn (scorn at scorn.net)'s article
> I too wonder how much work it would be to support OpenMP in gdc. From
> http://www.drdobbs.com/high-performance-computing/226300277 it seems to be that
> there is also quite a lot of magic on the compiler side (but which could
already
> be in the gcc parts). Maybe a concurrent garbage collector would also be needed
> (Leandro Lucarella worked on this for his diploma thesis).
> I hope someone can help to clear this up. If not OpenMP then at least a better
> support for multicore programming in one way or another will be really
important
> for the future of D.

Would take just a little bit of work, yes. ;)

Most of the heavy duty work for GCC OMP support is done by their own C
parser/internal codegen functions. So to start, will need to rewrite half of what
is there for the DMDFE AST.