[D-runtime] assocarray and array runtime interfaces

[Brad Roberts]

During the 64 bit work on dmd, Walter introduced a new set of api's to eliminate the use of variadic args.  However,
only 64 bit mode uses it currently.  I propose that the 32 bit interface also be changed over to the same api
and eliminate the old ones.

This is one of the areas that Iain raises in bug 5478 about differences between gdc and dmd.

I've done a test run with the new interfaces made unconditional in dmd and the old interface fully removed from druntime
with no ill effects to either 32 or 64 bit modes.

Here's the two branches:
  https://github.com/braddr/dmd/tree/remove-old-druntime-interface
  https://github.com/braddr/druntime/tree/remove-old-druntime-interface

Thoughts?

Later,
Brad