TODO

MDC:
	Unify: ArLZO and MDC::Filter::* ?
		they looks similar in purpose

CDB:
	use mmap in CDBRow as file-read-interface ?
	tests IRL required

	TL Narrow::operator() a bit slower (suprise)
	than empty implemntation:
	CDB/TL bench is a bit slower than trivial generic impl.

TL:
	rm Index::first_join

Bench:
	generate better data

Future:
	b+tree can performs better than std::map/set(rbtree)
	(stx-btree from idlebox.net) (much less cache misses)
	(it now packaged for debian in stx-btree-dev)

NOTES:
	we can't use ifstream: imposible to get eof() before actual attempt to read

AVX2?

PERF:
    test with i5 5257
    ./bin/bench-thread-cdb --bench --count 4 --thread 1 :   53M rows per second
    ./bin/bench-thread-cdb --bench --count 4 --thread 4 :  120M rows per second