Canonicalize NaN on the hppa architecture

Update obsolete comments.

Fix incorrect, confusing comment.

Add missing keywords "override".

https://llvm.org/bugs/show_bug.cgi?id=22354

At the time DisallowConstCopy was introduced, GCC 4.7 and Clang 3.2 refused to allow the non-const copy constructors to be defaulted inline. This must have been concluded to be a compiler bug, as GCC 4.8 and Clang 3.4 seem fine with it. So, we can clean this up.

Meanwhile, the above-linked Clang bug triggered when a DisallowConstCopy derivative is captured by value in a C++14 generic lambda. capnp::CallContext in particular tended to be hit by this a lot. The bug only affects non-default (or out-of-line default) copy constructors, and thus is conveniently sidestepped by this change.

Add simple convenience classes for using TwoPartyVatNetwork as client or server, since I find myself rewriting this code over and over.

AnyList::operator== is not inline but was declared as such. Also made formatting of operator declarations consistent.

Add equal / operator == method

Add thisCap() method to capability servers which returns a capability to itself. Remove CapabilityServerSet's weak pointers since this supersedes them.