In MySQL if a savepoint is missing, it means something
else (most likely DDL) triggered an implicit commit. In this
case rather than erroring, let's give a warning message
so it's possible to use the same codepath as a DB where
this actually works.
Adds ?? for interpolating identifiers in raw
statements. Also adds raw(sql, obj) for
named :key syntax. Alternatively, 🔑
(trailing colon) may be used to specify an
identifier as a parameter.
