(trunk) update web.h's API s.t. there's an explicit function to use when downloading webseed content.

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14070 f4695dd4-2c0a-0410-b89c-da849a56a58e
(trunk libT) #1079 'webseeds don't respect speed limits': fixed.


git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14071 f4695dd4-2c0a-0410-b89c-da849a56a58e