LLSD-14: Extract remaining conditional LLSD mbrs to namespace llsd.

Per Monty's code review, it's dubious practice to have a class in which
certain members are sometimes visible, other times not. If these were virtual
methods, or non-static data members, the error would be obvious -- but even
with static data members and non-virtual methods, it looks like an ODR
violation. Extract conditional methods as free functions, as in changeset
07cd70e75473.