Revert elf.c to 3d3c5a3a144dfd652eafae30fd9334e23f225f50

- Reverts all latest changes from pancake, montekki and lemonboy
- Aiming to stabilize the ELF parser for the release
- We loose support for syms in phdr bins
- We loose support for relocs
- But we get proper symbol names and tested in real demos which are now broken
- The branch `elf-ng` contains the latest code with all montekki's and lemon's work
- Once this new branch gets fully tested it will be merged into master
rbufread is now more strict
Reapply 5870b6376ce143efc62634ee23da4734127c48fc
ELF parser is now fuzzer-proof