- minimum key/val size is up to 8 bytes. now perf tests and stress tests have a consistent mechanism for generating keys and values, reducing headache.
- perf tests use a "main" function that generates tables based on the provided key/val size and compressibility, while stress (correctness) tests use a main function that generates tables with a provided (default in all cases, I think) key/val size and fully zero'd values, so the table is in the "correct" zero-sum state. previously this was causing perf tests to generate zer-valued rows always, no matter what row size you wanted or how much compressibility was requested, which clearly skewed performance results (ie: your 100 byte rows are only 8 bytes)
- renamed legacy NULL pointers to nullptr
- moved some "special" operations to the perf/stress tests that use them instead of the global header, to keep things more tidy.



git-svn-id: file:///svn/toku/tokudb@51258 c7de825b-a66e-492c-adef-691d508d4ae1