* guix/scripts/pack.scm (self-contained-tarball): Add #:localstatedir?
parameter and honor it.
(%options, show-help): Add '--localstatedir'.
(guix-pack): Honor it.
* gnu/build/install.scm (populate-single-profile-directory): Add
#:register? parameter and honor it.
* doc/guix.texi (Binary Installation): Use '--localstatedir' in
example.
(Invoking guix pack): Document it.