AFAICT that would break on-disk compatibility of pg_trgm GIST indexes.
I don't believe we have adequate evidence to justify doing that, and in any case it ought to be a separate patch rather than buried inside a mostly unrelated feature patch.
Ok. Actually, I don't think just increasement of SIGLENINT as a solution. I beleive that we need to have it as index parameter. I'll try to provide more of tests in order to motivate this.
