Fix for IE10's improved newline handling

[Jermolene]

TiddlyWiki contains a fix for IE's historical mishandling of newlines in <pre> blocks. Now that IE10 fixes the underlying problem the fix within TiddlyWiki needs to be made conditional.

See this discussion: https://groups.google.com/d/topic/tiddlywiki/FZyNmBSftHQ/discussion

[pmario]

This issue probably means code used here at:

https://github.com/TiddlyWiki/TiddlyWiki/blob/f9da92c048d224758070f1c8d55fe692de14ac48/js/FormatterHelpers.js#L67

It's probably valid. I'll label it "issue"