Implement druntime functions for allocating individual structs on the heap.

[schveiguy]

Filled out stub functions for _d_newitemT and _d_newitemiT. I noticed the typeinfo passed to these functions is still the "array of" typeinfo, but that is not a huge deal. However, it seems a little odd.

fix issue 7243 - Compiler should call separate function when allocating a struct on the heap

[dnadlinger]

Ping? Looks fine to me, the only thing I might change is to remove the pieces of code for the 0 size case, which are commented out anyway (OTOH, I'm not sure if they could ever be triggered, though).

[schveiguy]

I was waiting to hear back on pull request 556 for phobos

regarding the 0 size case, I wasn't sure if it was valid to receive a 0 size. For the array case, a 0 length was certainly possible. But a 0 size, I'm not sure.

And yeah, it's commented out, but I don't know if it will break anything when it's checked in :) I say leave it commented out, and then if nobody complains for a couple months, we can remove the comments.

[schveiguy]

Seems like this should be merged then, 556 was merged. I'll merge this and close the bugzilla issue.

It's failing freebsd, but so is everything else, looks like an error in the main line.