Teach readelf about some OpenBSD ELF program headers
- Add constants for OpenBSD wxneeded, bootdata and randomize to the FreeBSD elf_common.h file. This is the file that gets used by the elftoolchain library.
- Update readelf and elfdump utilities to decode these program headers if they are encountered.
Note: FreeBSD has it's own version of elfdump(1), which will be updated
in a subsequent commit. I am adding it here anyway because this diff is
going to be submitted upstream.
Discussed with: emaste
Reviewed by: imp
MFC afer: 2 weeks
Differential Revision: https://reviews.freebsd.org/D20548