Avoid sequencesize for more than 2000 statements.
Avoid sequencesize for more than 2000 statements.

It hardly saves any bytes for a sequence so long, and it risks blowing the
stack with the recursive Seq functions.

Ref #414

hychen/UglifyJS2,istr/UglifyJS2,butchi/decodecodeJS,HankMcCoy/UglifyJS2,sebmck/UglifyJS2,TurkeyFried/uglifyjs2-dist,rvanvelzen/UglifyJS2,vjeux/UglifyJS2,SpainTrain/UglifyJS2,microlv/UglifyJS2,shanaithal/UglifyJS2,githuboflee/first,davidbau/UglifyJS2,jchbh-duplicate/UglifyJS2,sielay/UglifyJS2,butchi/codedecodeJS,supriyantomaftuh/UglifyJS2,GerHobbelt/UglifyJS2,dabretin/UglifyJS2,avdg/UglifyJS2,kemitchell/UglifyJS2,VIVEKLUCKY1848/UglifyJS2,kittens/UglifyJS2,shelsonjava/UglifyJS2,digitalloggers/UglifyJS2,Jeremy017/UglifyJS2