tdb2: Add speed test to tdb and tdb2

Current results of speed test:
$ ./speed 1000000
Adding 1000000 records:  14726 ns (67244816 bytes)
Finding 1000000 records:  2844 ns (67244816 bytes)
Missing 1000000 records:  2528 ns (67244816 bytes)
Traversing 1000000 records:  2572 ns (67244816 bytes)
Deleting 1000000 records:  5358 ns (67244816 bytes)
Re-adding 1000000 records:  9176 ns (67244816 bytes)
Appending 1000000 records:  3035 ns (67244816 bytes)
Churning 1000000 records:  18139 ns (67565840 bytes)
$ ./speed 100000
Adding 100000 records:  13270 ns (14349584 bytes)
Finding 100000 records:  2769 ns (14349584 bytes)
Missing 100000 records:  2422 ns (14349584 bytes)
Traversing 100000 records:  2595 ns (14349584 bytes)
Deleting 100000 records:  5331 ns (14349584 bytes)
Re-adding 100000 records:  5875 ns (14349584 bytes)
Appending 100000 records:  2751 ns (14349584 bytes)
Churning 100000 records:  20666 ns (25771280 bytes)

vs tdb1 (with hashsize 100003):
$ ./speed 1000000
Adding 1000000 records:  8547 ns (44306432 bytes)
Finding 1000000 records:  5595 ns (44306432 bytes)
Missing 1000000 records:  3469 ns (44306432 bytes)
Traversing 1000000 records:  4571 ns (44306432 bytes)
Deleting 1000000 records:  12115 ns (44306432 bytes)
Re-adding 1000000 records:  10505 ns (44306432 bytes)
Appending 1000000 records:  10610 ns (44306432 bytes)
Churning 1000000 records:  28697 ns (44306432 bytes)
$ ./speed 100000
Adding 100000 records:  6030 ns (4751360 bytes)
Finding 100000 records:  3141 ns (4751360 bytes)
Missing 100000 records:  3143 ns (4751360 bytes)
Traversing 100000 records:  4659 ns (4751360 bytes)
Deleting 100000 records:  7891 ns (4751360 bytes)
Re-adding 100000 records:  5913 ns (4751360 bytes)
Appending 100000 records:  4242 ns (4751360 bytes)
Churning 100000 records:  15300 ns (4751360 bytes)