Initial check-in of partial application code.  New API macro APPLY.  New example benchmarks/test_map.

On yellow-eyed:

------ Config refcnt-opt ------
reverse              0:01.15
tak                  0:00.67
rfib                 0:00.15
exp3_8               0:00.21
tree_insert          0:00.43
tree_insert_32       0:00.42
------ Config gc-opt ------
reverse              0:00.72
tak                  0:00.84
rfib                 0:00.26
exp3_8               0:00.11
tree_insert          0:00.74
tree_insert_32       0:00.72
Minor cleanup related to SPRITE_INIT_* and SPRITE_DEL_* macros.