disallow creating an object with the name "anything"

[Spacechild1]

...because this would eventually override pd_objectmakers's anything method, essentially breaking the abstraction/external loading mechanism.
fixes #372

[millerpuckette]

This is an interesting way an extern could bring Pd to its knees - but it will always be possible
for unfortunatelt written externs to crash Pd so I think this doesn't need to be enshrined in code -
perhaps it's worth a warning in the externs howto instead.

[Spacechild1]

but it's quite easy for users to name one of their abstractions "anything", as this user did: #372
without knowing the internals of Pd, there's no way of knowing that this is not allowed...
Won't it be better to have this fixed?

[millerpuckette]

Ah, right, I hadn't caught on that even making an 'anything' abstraction would add a
new method. I wonder what other side effects we can expect from that... anyhow, I'm convinced
and have adopted this.