cassandra.thrift: add copyright and change notices
cassandra.thrift: add copyright and change notices

The Apache license requires us to make a note on any changed file.

tempbottle/scylla,asias/scylla,kangkot/scylla,scylladb/scylla,acbellini/scylla,senseb/scylla,respu/scylla,scylladb/scylla,justintung/scylla,linearregression/scylla,stamhe/scylla,eklitzke/scylla,aruanruan/scylla,victorbriz/scylla,duarten/scylla,avikivity/scylla,kjniemi/scylla,capturePointer/scylla,victorbriz/scylla,gwicke/scylla,duarten/scylla,asias/scylla,senseb/scylla,rluta/scylla,aruanruan/scylla,linearregression/scylla,dwdm/scylla,dwdm/scylla,rentongzhang/scylla,capturePointer/scylla,glommer/scylla,linearregression/scylla,raphaelsc/scylla,guiquanz/scylla,phonkee/scylla,rluta/scylla,bowlofstew/scylla,tempbottle/scylla,shaunstanislaus/scylla,rentongzhang/scylla,wildinto/scylla,glommer/scylla,respu/scylla,stamhe/scylla,senseb/scylla,avikivity/scylla,justintung/scylla,shaunstanislaus/scylla,wildinto/scylla,glommer/scylla,dwdm/scylla,raphaelsc/scylla,rentongzhang/scylla,scylladb/scylla,rluta/scylla,bowlofstew/scylla,kangkot/scylla,tempbottle/scylla,phonkee/scylla,wildinto/scylla,kjniemi/scylla,gwicke/scylla,gwicke/scylla,kangkot/scylla,acbellini/scylla,justintung/scylla,bowlofstew/scylla,asias/scylla,scylladb/scylla,phonkee/scylla,guiquanz/scylla,kjniemi/scylla,guiquanz/scylla,aruanruan/scylla,raphaelsc/scylla,shaunstanislaus/scylla,capturePointer/scylla,avikivity/scylla,eklitzke/scylla,stamhe/scylla,victorbriz/scylla,eklitzke/scylla,respu/scylla,acbellini/scylla,duarten/scylla