It should have been this way all along, and it seems I thought they were
when I did rua_gui.c as it already freed its resource block, which would
have been a double free (oops). Fixes an invalid write when shutting
down progs in qwaq-cmd (relevant change not committed).
This is meant for a "permanent" tear-down before freeing the memory
holding the VM state or at program shutdown. As a consequence, builtin
sub-systems registering resources are now required to pass a "destroy"
function pointer that will be called just before the memory holding
those resources is freed by the VM resource manager (ie, the manager
owns the resource memory block, but each subsystem is responsible for
cleaning up any resources held within that block).
This even enhances thread-safety in rua_obj (there are some problems
with cmd, cvar, and gib).
They take a pointer to a free-list used for hashlinks so the hashlink
pools can be per-thread. However, hash tables that are not updated are
always thread-safe, so this affects only updates. progs_t has been set
up such that it is easy for multiple progs within one thread can share
hashlinks.
