Kill a bunch of '=&' references for LinkCache, ParserCache, and MimeMagic singletons.

Kill a bunch of '=&' references for LinkCache, ParserCache, and MimeMagic singletons.
This is an old PHP 4-ism; only needed today if you want to be able to replace the singleton with another object by using the reference as an lval. :)
Killing them because they annoy me.