MINOR: replace acl_fetch_{path,url}* with smp_fetch_*

MINOR: replace acl_fetch_{path,url}* with smp_fetch_*

Doing so allows us to support sticking on URL, URL's IP, URL's port and
path.

Both fetch functions should be improved to support an optional depth
allowing to stick to a server depending on just a few directory
components. This would help with portals, some prefetch-capable
caches and with outgoing connections using multiple internet links.