Curl support RFC

[dsimcha]

I don't know much about this kind of stuff except that I use it for very simple
use cases occasionally.  One thing I'll definitely give your design credit for,
based on your examples, is making simple things simple.  I don't know how it
scales to more complex use cases (not saying it doesn't, just that I'm not
qualified to evaluate that), but I definitely would use this.  Nice work.

BTW, what is the license status of libcurl?  According to Wikipedia it's MIT
licensed.  Where does that leave us with regard to the binary attribution issue?

== Quote from Jonas Drewsen (jdrewsen at nospam.com)'s article
> Hi,
>     So I've spent some time trying to wrap libcurl for D. There is a lot
> of things that you can do with libcurl which I did not know so I'm
> starting out small.
> For now I've created all the declarations for the latest public curl C
> api. I have put that in the etc.c.curl module.
> On top of that I've created a more D like api as seen below. This is
> located in the 'etc.curl' module. What you can see below currently works
> but before proceeding further down this road I would like to get your
> comments on it.
> //
> // Simple HTTP GET with sane defaults
> // provides the .content, .headers and .status
> //
> writeln( Http.get("http://www.google.com").content );
> //
> // GET with custom data receiver delegates
> //
> Http http = new Http("http://www.google.dk");
> http.setReceiveHeaderCallback( (string key, string value) {
> 	writeln(key ~ ":" ~ value);
> } );
> http.setReceiveCallback( (string data) { /* drop */ } );
> http.perform;
> //
> // POST with some timouts
> //
> http.setUrl("http://www.testing.com/test.cgi");
> http.setReceiveCallback( (string data) { writeln(data); } );
> http.setConnectTimeout(1000);
> http.setDataTimeout(1000);
> http.setDnsTimeout(1000);
> http.setPostData("The quick....");
> http.perform;
> //
> // PUT with data sender delegate
> //
> string msg = "Hello world";
> size_t len = msg.length; /* using chuncked transfer if omitted */
> http.setSendCallback( delegate size_t(char[] data) {
>      if (msg.empty) return 0;
>      auto l = msg.length;
>      data[0..l] = msg[0..$];
>      msg.length = 0;
>      return l;
>      },
>      HttpMethod.put, len );
> http.perform;
> //
> // HTTPS
> //
> writeln(Http.get("https://mail.google.com").content);
> //
> // FTP
> //
> writeln(Ftp.get("ftp://ftp.digitalmars.com/sieve.ds",
>                  "./downloaded-file"));
> // ... authenication, cookies, interface select, progress callback
> // etc. is also implemented this way.
> /Jonas