Merge branch 'nd/shallow-fixup' into maint

Code cleanup in shallow boundary computation.

* nd/shallow-fixup:
shallow.c: remove useless code
shallow.c: bit manipulation tweaks
shallow.c: avoid theoretical pointer wrap-around
shallow.c: make paint_alloc slightly more robust
shallow.c: stop abusing COMMIT_SLAB_SIZE for paint_info's memory pools
shallow.c: rename fields in paint_info to better express their purposes

diff --cc shallow.c
Simple merge