* lisp/so-long.el: (so-long-statistics-excessive-p): New predicate
function using `buffer-line-statistics'.
(so-long-predicate): Use `so-long-statistics-excessive-p' by default.
* etc/NEWS: Describe changes.
* test/lisp/so-long-tests/so-long-tests-helpers.el:
* test/lisp/so-long-tests/so-long-tests.el: Update tests.
Also improve the existing `so-long-tests-predicate' tests.