Sereal::Merge: make strtable be more compact
Sereal::Merger: macroize srl_buf_cat_tag_nocheck
Sereal::Merger: revert 82d8f15

The changes I've made in 82d8f15 was completely stupid
Sereal::Merger: 010_desperate.t enable dedupe_strings test
Sereal::Merger: limit to hash/array to SRL_MAX_U32_VARINT_LENGTH items
Sereal::Merger: some code cleanup
Sereal::Merger: extend TODO list