* vendor newest libelf
source:
2d5b59c99a/libelf
* use exec_elf.h from openbsd to define structs
* libelf: build fixes
- do not link against muslc.
- windows and apple use bundled exec_elf.h.
- casts added like the old elf32.h, elf64.h and elf.c so pointer
arithmetic works. otherwise some compilers complain about void*.
- remove unused bits of exec_elf.h and added typedefs.
* adapt CMakeLists.txt to use libelf's CMakeLists.txt
* adapt reios_loadElf() to new libelf API