std.parallelism: Request for Review [Summary of discussion]

[dsimcha]

Ok, so that's one issue to cross off the list.  To summarize the discussion so
far, most of it's revolved around the issue of automatically determining how many
CPUs are available and therefore how many threads the default pool should have.
Previously, std.parallelism had been using core.cpuid for this task.  This module
doesn't work yet on 64 bits and doesn't and isn't supposed to determine how many
sockets/physical CPUs are available.  This was a point of miscommunication.

std.parallelism now uses OS-specific APIs to determine the total number of cores
available across all physical CPUs.  This appears to Just Work (TM) on 32-bit
Windows, 32- and 64-bit Linux, and 32-bit Mac OS.

We still need a volunteer to manage the review process.  As a reminder, for those
of you who have been meaning to have a look but haven't, the Git repository is at:

https://github.com/dsimcha/std.parallelism

The pre-compiled documentation is at:

http://cis.jhu.edu/~dsimcha/d/phobos/std_parallelism.html