Remove useless unwind-protect forms, or make them useful as intended

Remove useless unwind-protect forms, or make them useful as intended

* lisp/imenu.el (imenu--generic-function):
* lisp/mail/yenc.el (yenc-decode-region):
* lisp/textmodes/table.el (table-recognize-region):
* test/lisp/dired-tests.el (dired-test-directory-files):
* test/lisp/hl-line-tests.el (hl-line-tests-sticky):
Fix unwind-protect bracketing mistakes that caused the unwind code to
be misplaced.
* lisp/strokes.el (strokes-read-stroke): Fix a bracketing mistake that
misplaced the unwind code, and another one that misplaced the
else-clause of an `if` form.
* test/lisp/gnus/mml-sec-tests.el (mml-secure-test-fixture): Fix a
bracketing mistake that misplaced the unwind code, and remove
superfluous condition-case.

* lisp/mwheel.el (mouse-wheel-global-text-scale):
* lisp/speedbar.el (speedbar-stealthy-updates)
(speedbar-fetch-dynamic-etags):
* lisp/emacs-lisp/edebug.el (edebug--recursive-edit):
* lisp/emacs-lisp/package.el (package--read-pkg-desc):
* lisp/cedet/semantic.el (semantic-refresh-tags-safe):
* lisp/emulation/viper-cmd.el (viper-escape-to-state):
* lisp/emulation/viper-cmd.el (viper-file-add-suffix):
* lisp/gnus/mail-source.el (mail-source-movemail):
* lisp/mail/feedmail.el (feedmail-send-it-immediately)
(feedmail-deduce-address-list):
* lisp/mail/mailclient.el (mailclient-send-it):
* lisp/mail/smtpmail.el (smtpmail-deduce-address-list):
* lisp/mh-e/mh-print.el (mh-ps-print-range):
* lisp/textmodes/reftex-index.el (reftex-index-this-phrase):
* test/lisp/emacs-lisp/ert-tests.el (ert-test-run-tests-batch):
(ert-test-run-tests-batch-expensive):
Remove unwind-protect forms that are apparently useless, some since a
prior edit that removed their purpose, some since their first
appearance.

* test/lisp/subr-tests.el (subr-test--frames-2):
Insert dummy unwind form in backtrace test code.