Fix port syntax in host header of HTTP requests.

When constructing a host header, if PORT is an integer, add it to the
header, otherwise omit it.

The previous behavior resulted in host headers like
"www.example.com:NIL", which failed on S3 but (confusingly) worked on
CloudFront.

Author: xach

quicklisp/http.lisp

@@ -365,8 +365,9 @@ information."
              (apply #'add-strings sink strings)
              (add-newline sink)))
       (add-line method " " path " HTTP/1.1")
-      (add-line "Host: " host (if (eql port 80) ""
-                                  (format nil ":~D" port)))
+      (add-line "Host: " host (if (integerp port)
+                                  (format nil ":~D" port)
+                                  ""))
       (add-line "Connection: close")
       (add-line "User-Agent: " (user-agent-string))
       (add-newline sink)