>> Introduce dynamic shared memory areas.
gaur finds another problem with dsa.c: it uses SIZE_MAX which AFAICS
is not required to exist by POSIX.
We could adopt the timezone code's workaround
#ifndef SIZE_MAX
#define SIZE_MAX ((size_t) -1)
#endif
but I don't find that particularly nice, and in any case I wonder
why we would want to use SIZE_MAX and not MaxAllocHugeSize. The
overflow hazards that motivate that not being the max possible
value seem relevant here too.
regards, tom lane
