VSIX tooling changes to support Visual Studio 2013.
Use the target platorm version in the VS props file as well.
Update comments and package flavor error message.
More changes to support MSVC 18.
Use the VisualStudioVersion variable instead of _MSC_VER.
More corrects to VS 2013 integration.
Environment variable names in nmake must be in all uppercase.
Initial implementation of the unlikely() SQL function used as a hint to
the query planner.
Enhance the plan solver to take into account the number of output rows when
computing the set of paths to retain for the next cycle.
Continuing refinements of the logic to take WHERE clause terms not used for
indexing into account when computing the number of output rows from each
table.
Merge trunk fixes into the unlikely-func branch.
Tweaks to the index selection logic.
Change the name of the two-argument unlikely() function to likelihood().
Add test cases.
Additional unlikely() test cases.  Logic tweaks to support test coverage.
Improvements to likelihood processing so that commuting an unindexed term in
the WHERE clause does not change the query plan.
Merge updates from trunk.
Increase the number of bits available in Expr.flags.  Other tweaks aimed at
making expression processing more robust.
Merge in the Expr.flags expansion to 32-bits.  Use an extra bit to help
optimize the sqlite3ExprSkipCollate() routine.
Refactor the ExprSetIrreducible() macro into ExprSetVVAProperty(*,EP_NoReduce).
This is a naming change only.  The logic is the same.
Add tests for the fts4 unicode61 tokenchars and separators options.