Improve the accuracy of the estimates used when searching an index for values not present in any stat4 samples under some circumstances.
Fix a division-by-zero error that might occur if the sqlite_stat1 table is corrupt.
Avoid leaking Index.aiRowEst memory if an OOM causes a rollback which deletes
the index before the aiRowEst deletion code in sqlite3AnalysisLoad() routine
has a chance to run.  Since the aiRowEst now might be deleted from freeIndex()
which does not always have a db pointer, make sure the aiRowEst memory is
not held in lookaside.
Add a test to show that the change on this branch is effective.
Fix a harmless compiler warning inside an assert() in FTS4.
Improve the accuracy of the estimates used when searching an index for values not present in any stat4 samples.
Remove unreachable branches in decodeIntArray() when compiling without
STAT3 or STAT4.