The deferred-FK DDL rewrite dropped any SHOW CREATE TABLE line containing
" FOREIGN KEY ", including column definitions whose COMMENT text merely
mentions the words; it now strips only genuine CONSTRAINT ... FOREIGN KEY
constraint lines. Structure-only transfers onto a preexisting target table
skipped the incompatible-structure validation that data transfers perform
and reported success while the target kept missing source columns; the
check now runs on both paths.
Closes#7660
t8y2