Bugzilla Bug 191550

I recently added support for building the python bindings in net-snmp to
net-snmp-5.4.1, but without adding the DEPEND on dev-python/setuptools - my bad
there.  Once I added the dep, I found that dev-python/setuptools isn't
keyworded for mips.

For now, I've drop ~mips from net-snmp-5.4.1-r1 (the only difference between it
and 5.4.1 is the python bindings), but I don't want this to be the case going
forward.

Would there be a problem keywording setuptools for mips?  This seems to be the
most straightforward solution, unless I'm missing something, which I may be. 
Once that's done, I can re-add ~mips to net-snmp-5.4.1-r1.

If setuptools can't be keyworded for mips, I'll be happy to examine other
options (such as patching setup.py to use stock distutils or something).

Marked unstable.