Merge branch 'master' into topic/constructor_rewrite
Fix test description (DrHyde++)
Normalize varnames (zero functional changes)
Reorder prefetch logic for optimal execution (no functional changes)

Avoid yet another expensive try call
Stop needlesly invoking the $rs bool overload
Another parser microoptimisation - lose nullability checks where possible
space-compress tests making them readable - no changes
Use the defined-or operator in generated code on newer perls

Even *less* expensive op ;)
Consider where condition when determining leftmost order stability

Extract more eyebleed into DBIHacks in the process
Recognize root source unqualified columns under limited prefetch