Escape delimiter in SpecialPage::prefixSearchArray

Changed preg_quote() call so that the proper delimiter
is passed as the second parameter, thus making sure
it is properly escaped.

Change-Id: Ie12418e5433642b86dcda425b63a05ac3ff2c29d
Merge "Escape delimiter in SpecialPage::prefixSearchArray" into wmf/1.24wmf11