MINOR: pools: replace DEBUG_MEMORY_POOLS with runtime POOL_DBG_TAG

This option used to allow to store a marker at the end of the area, which
was used as a canary and detection against wrong freeing while the object
is used, and as a pointer to the last pool_free() caller when back in cache.
Now that we can compute the offsets at runtime, let's check it at run time
and continue the code simplification.
3 files changed