Improved "wheretrace" capabilities:  Show the constraint expression if the
wheretrace flag has the 0x100 bit set and if compiled with
SQLITE_ENABLE_TREE_EXPLAIN.
Bug fix and enhancements to the improved wheretrace logic that shows the
constraint expressions.
More wheretrace debugging support:  Show a listing of all WHERE clause
terms (on wheretrace bit 0x100) and include important flags such as
TERM_VIRTUAL, WO_EQUIV, and EP_FromJoin.
Do not use transitive WHERE-clause constraints on LEFT JOINs.
Fix for ticket [c620261b5b5dc].
Add regression tests for ticket [c620261b5b5].
Formatting improvements to the WHERE-clause constraint display in the
wheretrace debugging logic.