Add elf
Add elf

Add `elf` package (v0.29)
stackbuilders/stackage,soenkehahn/stackage,creichert/stackage,clinty/stackage,jonschoning/stackage,Shimuuar/stackage,Daniel-Diaz/stackage,athanclark/stackage,fimad/stackage,michalkonecny/stackage,wereHamster/stackage,mstksg/stackage,spencerjanssen/stackage,simonmichael/stackage,ethercrow/stackage,peti/stackage,mrkkrp/stackage,massysett/stackage,asr/stackage,int-index/stackage,iand675/stackage,fpco/stackage,mgajda/stackage