Adding relocation tables to executables

[ddevault]

In-place relocation is convenient for assembly programmers but a more robust solution would be the traditional relocation tables found in other executable formats like ELF. Adding this would be convenient for C programs as well and would help us simplify the compiler.

1. Add a new KEXC header which points to a relocation table, simply a list of program-relative addresses at which additional program-relative addresses can be found within the code (terminated with a null word)
2. Update the kernel loader to recognize this and relocate programs when loading them
3. Update scas to emit one of these

[pixelherodev]

The second stage is to then update all existing packages to use the relocation table and remove in-place relocations from the toolchain entirely.

[pixelherodev]

This also requires updating the documentation (AFAIK, none is currently out of date enonugh to be problematic, and I'd rather keep it that way).