README, debian/control: Deprecate `sox' support.

README, debian/control: Deprecate `sox' support.

sox introduced yet more command-line options in 14.2, whinges about the
old ones in 14.4, and threatens to remove them in 14.5 (because
obviously compatibility between minor versions is an old-fashioned idea
whose day is long past).

Rather than chase this obnoxiously moving target,

  (a) report that sox support is deprecated and will be removed in some
      future major version of DisOrder; and

  (b) have the Debian package Build-Depend on `libsamplerate0-dev' so
      that at least Debian users don't have to put up with sox's moaning
      in the logs.

Reported-by: Ross Younger