Tail call optimisation not explicitely guaranteed by the manual

[Ekdohibs]

After searching the entire manual, I wasn't able to find a guarantee that tail call optimisation occurs (searching for keywords tail call, last call, tailcall and lastcall). It is often discussed in the context of other features as if it was obviously present, but there is no explicit guarantee.

[lthls]

I'm aware of two indirect references: the section on builtin attributes mentions it, as well as the section on tail mod cons. Both of those could benefit from a dedicated section to link to.