Severity: wishlist

The variable `small-temporary-file-directory` was created in 2000 for
MS-DOS systems and systems with widely different specs than what we run
now.  Putting temporary files on a RAM disk should be done by the system
administrator (usually the user themselves), for example by simply using
tmpfs for _all_ temporary files (not just "small" ones, whatever that
means).

I think the variable doesn't make much sense these days, and should be
made obsolete.  Note that it is barely used in Emacs and third-party
packages.

However, Tramp recently started using the variable as a place to create
OpenSSH Unix domain sockets.  May I suggest that Tramp uses some other
variable for this purpose, perhaps a Tramp specific one?

I've attached a diff that makes the variable obsolete and removes all
uses, for reference.