If you have optional<T> x, y;  x = *y;  guarantee(x);, it is a sign
that you did not mean to dereference y.  It also means the unchecked
deref was supposed to be safe.

Avoids a clang warning about (potentially) misaligned
pointers.

Silences a new clang warning on out-of-range truncation.

Naming the file memory.hpp caused some files that #include "memory.hpp" to
include the wrong file on Windows, because another file in a subfolder
has that name.  So we name it memory_utils.hpp.

function.hpp was not included anywhere, and boost::function was
only used in some unit test code.

(This fixes the problem where you grep the source code for val_t
and get this stuff.

This way we can name the parameter names after we make mailbox_t
no longer take a function type parameter.

This is to make contributing more accessible to newbies, since there's
not a company anymore.

Apparently these have been failing since write hooks were
implemented.

Less interface to maintain, uses unordered_map, and we no longer
allocate a new list node and copy the key/value every time we do a
lookup.