It's a bit fishy for oop/oopDesc to have knowlege about the subclasses of InstanceKlass, as provided via the is_instanceXXX suite of functions (is_instanceRef, is_instanceMirror, is_instanceClassLoader). There are also very few uses of these functions. So we should just remove them.

There are:
Two uses of is_instanceRef, both in assertions.
One use of is_instanceMirror.
No uses of is_instanceClassLoader.

Also remove the unused (and in some cases misspelled) is_instanceRef_noline, is_instanceMirror_noinline, and is_instanceClassLoader_noline. [These also use the unsuffixed functions, but I didn't include them in the above counts, since none of these are used.]