diff UNIT_TEST_LSH.cpp @ 302:74824093c1c4

Implement O((M+N) log(M+N)) duplicate key detection in batchinsert,
rather than naive O(N^2).

Note that I haven't measured the constants in those complexity
expressions; I am anticipating that 40000 is a sufficiently large N for
this to matter.

Write a test case for duplicate keys, too.  Use 0037, since no-one else
seems to be writing tests, and everything is merged onto the trunk these
days anyway.