Optimizations for memory-tight systems.
Check all previous gaps first for any usage, so gaps we created when
faced with perhaps a relatively large allocation that left a lot of
the last chunk on the table can be backfilled with smaller things as
it goes on.
Separate the members that only live in the head object out of the
buffer management object, reducing the cost of new chunks. Allocate
the head object members as the first thing in the first chunk, and
adjust all the code to look there for them.
Add lwsac helper api to allow user code to perform constant string folding
easily within an lwsac. After isolating a string or blob that it wants to store in
the lwsac and point to, it can check if the string or blob already exists earlier
in the lwsac first, and if so just point to that without copying it in again.
For some formats with repeated strings like JSON, the saving can add up to
something useful.
