To comply with RFC 8212 requirements.

Old way to set direct routes is to use local IP as gateway, but that does
not work properly on newer FreeBSDs. Now we use sockaddr_dl containing
interface index as gateway.

Multiple definitions of same channels are forbidden, but inherited
channel can be redefined. In such case channel options are merged.

Function filter_same() must be called with arguments in proper order,
otherwise it breaks the new filter, causing crash during route
processing.

The same is already done for clists. Also fixes defined() to work
properly for paths and clists.

Should use remote value, not local value.

According to GNU Readline developers, if we link with libreadline then
there is no need to link with libhistory at all.

Based on patch from Pavel Tvrdik

Also change linpool.current ptr to really point to thr current chunk.

Old code breaks with some versions of bison