Initial check-in of a test VFS designed to simulate a NAND-flash SSD for the
purpose of measuring and subsequently minimizing write amplification caused
by SQLite.  The code in this check-in compiles but does not run.
Merge the command-line shell enhancements from trunk.  Other edits toward
trying to get ssdsim to run.
Further work on getting ssdsim to run.  This is an incremental checkin to
save my place while jumping off to work on other things.