Bug 11322: fix XSS bug in purchase suggestions pages

Bug 11322: fix XSS bug in purchase suggestions pages

To test
1/ Switch on purchase suggestions
2/ On the public interface (OPAC) add a suggestion, put html in every
field
3/ In the staff interface go to the suggestions page
/cgi-bin/koha/suggestion/suggestion.pl
4/ Notice the html is rendered
5/ Click on a suggestion, notice the html is rendered on the show page
also
6/ Apply the patch, check these two pages again, html should now be
escaped

Signed-off-by: David Cook <dcook@prosentient.com.au>
Works as described.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests, thx Chris!

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 368068c71597eaf61e4f9cc154002ea92dfd16c3)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>