Correct input-placeholder stats for Opera 11.50

Opera 11.50 also supports the placeholder attribute on <textarea>. This
was determined using Opera 11.50 on Windows 7 installed with the archived
installer: http://arc.opera.com/pub/opera/win/1150/en/Opera_1150_en_Setup.exe
and a jsFiddle: http://jsfiddle.net/qmdxjro0/
Screenshot: http://i.imgur.com/bfsxm80.png
Merge pull request #699 from dtrebbien/master

Correct input-placeholder stats for Opera 11.50