sstring: fix truncation in compare()
sstring: fix truncation in compare()

If the difference between the sizes of the two strings is larger than can
be represented by an int, truncation will occur and the sign of the result
is undefined.

Fix by using explicit tests and return values.

tempbottle/scylla,koolhazz/seastar,bowlofstew/scylla,phonkee/scylla,flashbuckets/seastar,aruanruan/scylla,tempbottle/seastar,justintung/scylla,koolhazz/seastar,asias/scylla,sjperkins/seastar,leejir/seastar,dreamsxin/seastar,bowlofstew/scylla,sjperkins/seastar,kangkot/scylla,glommer/scylla,glommer/scylla,dreamsxin/seastar,leejir/seastar,raphaelsc/scylla,senseb/scylla,avikivity/seastar,flashbuckets/seastar,anzihenry/seastar,bowlofstew/seastar,xtao/seastar,joerg84/seastar,leejir/seastar,linearregression/seastar,mixja/seastar,flashbuckets/seastar,avikivity/scylla,joerg84/seastar,raphaelsc/seastar,victorbriz/scylla,respu/scylla,mixja/seastar,duarten/scylla,rentongzhang/scylla,cloudius-systems/seastar,scylladb/scylla-seastar,shyamalschandra/seastar,acbellini/seastar,rentongzhang/scylla,mixja/seastar,norcimo5/seastar,slivne/seastar,kjniemi/scylla,capturePointer/scylla,acbellini/seastar,wildinto/seastar,chunshengster/seastar,rentongzhang/scylla,capturePointer/scylla,ducthangho/imdb,avikivity/scylla,guiquanz/scylla,stamhe/seastar,rluta/scylla,slivne/seastar,xtao/seastar,shyamalschandra/seastar,phonkee/scylla,shaunstanislaus/scylla,xtao/seastar,raphaelsc/seastar,glommer/scylla,wildinto/seastar,eklitzke/scylla,aruanruan/scylla,chunshengster/seastar,bowlofstew/seastar,dwdm/seastar,bowlofstew/seastar,justintung/scylla,linearregression/seastar,scylladb/scylla-seastar,anzihenry/seastar,syuu1228/seastar,guiquanz/scylla,shaunstanislaus/scylla,kjniemi/scylla,jonathanleang/seastar,wildinto/scylla,joerg84/seastar,gwicke/scylla,victorbriz/scylla,tempbottle/seastar,tempbottle/scylla,asias/scylla,scylladb/seastar,hongliangzhao/seastar,raphaelsc/scylla,dwdm/scylla,stamhe/scylla,printedheart/seastar,koolhazz/seastar,raphaelsc/seastar,ducthangho/imdb,justintung/scylla,acbellini/scylla,senseb/scylla,victorbriz/scylla,printedheart/seastar,scylladb/scylla,stamhe/seastar,linearregression/scylla,shaunstanislaus/scylla,wildinto/scylla,stamhe/scylla,dwdm/scylla,syuu1228/seastar,norcimo5/seastar,wildinto/scylla,tempbottle/scylla,kjniemi/seastar,respu/scylla,slivne/seastar,chunshengster/seastar,stamhe/scylla,phonkee/scylla,duarten/scylla,gwicke/scylla,anzihenry/seastar,cloudius-systems/seastar,scylladb/seastar,bzero/seastar,linearregression/scylla,shyamalschandra/seastar,aruanruan/scylla,avikivity/seastar,jonathanleang/seastar,acbellini/seastar,senseb/scylla,kjniemi/scylla,scylladb/scylla-seastar,dwdm/scylla,sjperkins/seastar,cloudius-systems/seastar,kjniemi/seastar,bzero/seastar,avikivity/scylla,raphaelsc/scylla,duarten/scylla,norcimo5/seastar,scylladb/seastar,respu/scylla,ducthangho/imdb,hongliangzhao/seastar,hongliangzhao/seastar,jonathanleang/seastar,bzero/seastar,gwicke/scylla,acbellini/scylla,printedheart/seastar,scylladb/scylla,wildinto/seastar,linearregression/scylla,tempbottle/seastar,bowlofstew/scylla,stamhe/seastar,rluta/scylla,dreamsxin/seastar,dwdm/seastar,kangkot/scylla,guiquanz/scylla,linearregression/seastar,avikivity/seastar,rluta/scylla,scylladb/scylla,kjniemi/seastar,eklitzke/scylla,capturePointer/scylla,scylladb/scylla,acbellini/scylla,syuu1228/seastar,kangkot/scylla,eklitzke/scylla,asias/scylla,dwdm/seastar