std.http: add connection pooling, handle keep-alive and compressed content

[truemedian]

The connection pool is implemented as a TailQueue linked list, as there shouldn't be too many connections to loop over.

This should also fix a few problems that people were having where the server would try to read more data than the server was sending, leaving them in a deadlock.

Redirected requests now always read the content associated with the redirect, but the data is voided. This is required to prepare the connection for another request (but could potentially be avoided on a Connection:close)

[alichraghi]

test-filetimestamp.tmp what's this? lol

[truemedian]

Really good question, not sure how I missed that or what that came from.

[kcbanner]

Really good question, not sure how I missed that or what that came from.

I've seen that file sometimes get leftover by running the tests.

[andrewrk]

It looks good; I'd like to merge it.

How have you been testing it? Do you have any inclination to help out with adding a testing system for this stuff?

[truemedian]

I've currently been testing the new features against http://httpbin.org (in http, to bypass all of the tls bugs in std.crypto). I can't really fuzz it against anything but it has worked for all of the things I've tested it against.

I don't see a way to seriously test std.http.Client without first implementing a std.http.Server to test against.