clib2 Code

- Added the __decay_unused_slabs() function which brings all currently
empty slabs which are still protected from reuse closer to getting
reused or released.

- The slab-test program now exercises the memory allocation functions
to a greater degree. Memory is allocated in random chunk sizes,
the allocations are resized (to other random chunk sizes),
33% of all allocations are randomly freed, empty slabs readied for
reuse then discarded. The output in JSON format now shows a bit
more information as to what is being done.

- Rewrote __get_slab_stats() to use setjmp() and longjmp() in the
print() callback invocation.

- __get_slab_stats() now reports how many times a slab was reused
after having stuck around in the "empty slab" list.

- Changing the slab size through an environment variable is now
a feature of the debug build.

- Small changes to allow the library to be built with SAS/C again.
This includes adding code to disable/re-enable profiling,
fixing "stdlib_profile.h" and updating the smakefiles.

- Still not sure what it does, but _CXV45 now sits along with _CX25
and _CX35 in "sas_cxv.asm". "sas_cxv54.asm" is not needed any
more.

- Found the last use of MEMF_PRIVATE which should have been compiled
only for the OS4 version.