Further refinement of the idea of multiplying run-time cost estimates by
the estimated row size.
Use #ifdefs to omit unused code in the columnType() routine depending on
compile-time options.
Rollback some of the previous changes in the branch such that the estimated
row sizes are now only used as a tie-breaker for index scans.
Fix test cases for the new information in PRAGMA index_list.
Move a conditional inside of an #ifdef in order to make all branches
reachable regardless of compile-time options used.