[Ur] Request environment variables

[Edward Z. Yang]

Hello all,

Servers pass a lot of interesting information to the CGI
programs in the form of environment variables (for example,
if you do client cert authentication, that info comes in the
form of an environment variable.)  It would be great if
Ur/Web could access that information.

Now, implementing this requires a little bit of cooperation
from the SAPIs, since, for example, FastCGI passes in its
environment variables from the wire, so just calling getenv
doesn't work.  But probably a 'getenv : string -> transaction string'
would work reasonably well.

Thoughts?

Cheers,
Edward