[phobos] crc32 module

[Alex Rønne Petersen]

Hi,

What are going to do about this one? I have two concerns:

1) It doesn't seem to be Boost-licensed.
2) It's in the global package namespace. Bad bad bad.

I don't think (1) is going to be a problem in practice (the license it
does have is fairly permissive). (2) on the other hand is annoying.
Could we copy it into std/crc32.d and deprecated crc32.d?

Regards,
Alex