Add `map64_customMalloc` (#2764)

Most allocations target ~56 bytes, causing internal fragmentation
in `map128_customMalloc`. Introduce `map64_customMalloc`, a
64-byte–chunk variant of `map128_customMalloc`. The new allocator
uses a `uint16_t` “map” array: each bit in a 16-bit entry tracks
the in-use status of one 64-byte chunk (16 chunks per map entry).
The bitmap region is fixed at 256 bytes. Note that “map” here is a
fast-lookup structure, distinct from the bitmap itself. All chunk-
size, shift, and map-size calculations have been updated
accordingly.

Relates to #2740

0 files changed, 0 insertions, 0 deletions