Memory Arenas and Concurrent Bitmaps

• arena.c: Arena creation, reservation, traversal, and destruction.
• arena-alloc.c: Allocation, freeing, commitment, and purging of arena slices.
• arena-page.c: Allocation, abandonment, reclamation, and freeing of pages backed by arena slices.
• arena.h: Private arena declarations, traversal callbacks, and layout helpers.
• bitmap.c: Concurrent bitmap searches and range operations; these bitmaps are used to manage the slices in an arena.
• bitmap-chunk.c: Bitmaps consist of 512-bit chunks; this provides the low-level atomic bit-field and bitmap-chunk operations.
• bitmap.h: Bitmap types, constants, and operation declarations.
• bitmap-chunk.h: Private declarations and iteration helpers for bitmap fields and chunks.