fix(http): use the right protocol for proxies

Previously, if doing a request to http://website.example.org
 through https://proxy.example.org, luasocket wouldn't use TLS
 and vice-versa

src/http.lua

@@ -62,7 +62,7 @@ local function receiveheaders(sock, headers)
         -- unfold any folded values
         while string.find(line, "^%s") do
             value = value .. line
-            line = sock:receive()
+            line, err = sock:receive()
             if err then return nil, err end
         end
         -- save pair in table
@@ -293,7 +293,9 @@ local function adjustrequest(reqt)
     end
 
     -- ajust host and port if there is a proxy
-    nreqt.host, nreqt.port, nreqt.create = adjustproxy(nreqt)
+    nreqt.host, nreqt.port, proxy_create = adjustproxy(nreqt)
+    if not reqt.create then nreqt.create = proxy_create end
+
     return nreqt
 end