* slime-tests.el: Break long lines.
Fix display related bugs.

* slime-tests.el (display-region):  New test.
(slime-test--display-region-line-to-position)
(slime-test--display-region-eval-arg): New Helpers.

* slime.el (slime--display-region): Renamed from slime-recenter.
Also work in the case when the condition message takes up the
entire window.
(slime--adjust-window-start, slime--adjust-window-point): New
helpers.
(slime-show-source-location): Display buffer in other window, as
it always was.  Invert no-highlight-p argument to simplify
callers.  Add recenter-arg to get rid of the heuristic that
detected "sldb show source" vs. "show definition".
(slime--display-position): Factored out, again.
ChaneLog entry for last few changes.