tsearch2 changes need backpatching?

The buildfarm member penguin (Debian, ARM) has been building the HEAD
branch for the most part happily since late January, but keeps failing
on the REL8_0_STABLE branch on tsearch2. It appears that some changes
made around 24-27 January fixed it for this architecture/OS. Looking in
the committers log, I see:

improve support of agglutinative languages (query with compound words)

and

Change
typedef struct {} WordEntryPos;
to
typedef uint16 WordEntryPos

Could one of these inadvertantly fix the problem we are seeing here? Do we need to backpatch to fix REL8_0_STABLE, or apply some other fix?

cheers

andrew