Fix Bug 752466, open plugincheck links in new tab

@pmclanahan r? So long story. I have been looking at this bug on and off, uncertain whether to close it as won't fix and tell the users to just right click or, to go ahead and fix it.

Well, I fixed but, I ended up using the simplest solution which, according to this [http://www.w3.org/TR/html5/browsers.html#valid-browsing-context-name-or-keyword] is still totally valid however, is this frowned upon and should not be done? If so, is there a different way we should handle this, with JS perhaps? Thoughts? Thanks!