Revert "Changed URL for curl downloading"

Curl component was modified because of url not working. Changing it back
to original url.
This reverts commit 4cae8f81.

component/curl/buildout.cfg

@@ -11,7 +11,7 @@ parts =
 
 [curl]
 recipe = hexagonit.recipe.cmmi
-url = http://www.gknw.de/mirror/curl/source/curl-7.21.3.tar.bz2
+url = http://curl.haxx.se/download/curl-7.21.3.tar.bz2
 md5sum = 5b57fee22090b5c43a6886fdd35af2ce
 configure-options =
   --disable-static