Migrate available block list to CK_LIST.
New blocks are only allocated when the available list is exhausted.
Remove bag->avail_tail.
Print out number of writer iterations for unit test.
Lengthen duration of unit test.
Add necessary load fence to iterator.
Initialize iterator appropriately for empty bags.
Improve unit test.
Fix bag linkage bug for non x86_64 targets.
Fix block accounting on removal.