Reverted trunk r12255 changes. Provided a portable flexible arrays replacement.

Reverted trunk r12255 changes. Provided a portable flexible arrays replacement.

Trunk r12255 made Clang compiler happy by removing flexible nonPod[] arrays.
Unfortunately, it also moved shared memory items into local memory (in some
cases uninitialized).

This change provides a Clang-friendly flexible array replacement while keeping
items in the shared memory (and using placement-new initialization). The code
may have become even less readable, but hopefully more portable.

N.B. Flexible arrays were introdiced in C99 standard, after C++ was
standardized in 1998. They are not yet in any revised C++ standard, but most
C++ compilers support them, at least for PODs.