[phobos] d2 64 bit update

[Brad Roberts]

I just checked in a slew of changes.  These bring druntime and phobos up 
to the point that running the tests pass.  However, I did that by 
disabling (for 64 bit only), all the tests that fail.  This is basically 
what the auto-tester has been doing for a while now.  At this point, 
anyone can replicate those builds, which is handy.

That said, it's still not up to the point of being useful for anything.  
Optimized builds are much worse off than non-opt builds.  The GC is broken 
in as-of-yet uninvestigated ways.  Without optimizations, about 2/3 of 
both the phobos tests and the dmd tests pass.  With optimizations, less 
than half.

If anyone is interested in helping, the biggest things I'd really like to 
see:

1) druntime's tests changed to be like phobos'.  In other words, one test 
app per .d file.  This makes it so much simpler to dig into what's going 
wrong.  Before anyone takes this as a point of failure of D's unittests, I 
think bootstrapping from totally broken is a very different case from a 
mostly working setup and digging into new issues.

2) implement the asm code in std/math.d.  

3) dig into the gc and figure out what's broken.  I believe walter has the 
d1 gc working, but I haven't spent any time looking at the changes there.  
There's enough differences that it likely won't be directly mergable and 
won't be complete.  A good start would be the dmd tests runnable/testgc* 
or possibly runnable/wc*.

Keep in mind that we're still fixing all three layers at the same time.  
Any one of which can be at fault for any failure.

Later,
Brad