Add test cases showing the use of ORDER BY on a recursive query to control
depth-first versus breath-first search of a tree.
Add test cases that compare the performance of the transitive_closure
virtual table again common table expressions for walking a tree.
Add a few more CTE test cases to closure.test.
Use an unsigned integer to accumulate the string hash.  Avoids compiler
warnings.
Add test cases for LIMIT and ORDER BY on recursive CTEs.
Fix harmless compiler warnings in the Tcl interface.
Select collation sequences for ORDER BY expressions attached to recursive CTEs in the same way as they are selected for other compound SELECT statements.
Fixes for various clang warnings.