cperl-mode.el: Optionally treat trailing text as comment

cperl-mode.el: Optionally treat trailing text as comment

* lisp/progmodes/cperl-mode.el (cperl-fontify-trailer): New
customization variable.  With a value of 'comment, cperl-mode
treats trailing text after after __END__ and __DATA__ as comment,
like perl-mode does (Bug#66161).
(cperl-find-pods-heres): Treat trailing text after __END__ and
__DATA__ according to the customization variable
`cperl-fontify-trailer'.

* test/lisp/progmodes/cperl-mode-tests.el (cperl-test-bug-66161):
New test, verifying the changed behavior if the custom variable is
set to 'comment.

* test/lisp/progmodes/cperl-mode-resources/cperl-bug-66161.pl: New
resource file, source code from the corresponding bug report.