method_util.{c,h}

[Leopold Toetsch]

While grepping through the src tree, I found this:

* all functions from method_util.c are unused and commented out
* method_util.h is included by several PMCs as well as other files
- this looks like c&p cruft
- the only used bits from this header is the definition of
C<Parrot_csub_t>, which is a function pointer that isn't used either as
such.
It's just casted forward and back from C<funcptr_t> (another function ptr).

If no one has objections, I'll remove all. It's just confusing and
misleading, when you e.g. grep the src for 'stash'.

leo