Unify GREEDY_REALLOC and GREEDY_REALLOC_T

greedy_realloc() and greedy_realloc0() now store the allocated
size as the count, not bytes.

Replace GREEDY_REALLOC uses with GREEDY_REALLOC_T everywhere,
and then rename GREEDY_REALLOC_T to GREEDY_REALLOC. It is just
too error-prone to have two slightly different macros which do the
same thing.