Elf36 Specification:

- Do we want to adjust SHN_LORESERVE up to SHN_HIRESERVE, including SHN_XINDEX, to
  account for the fact that we have 2 more bits available in Elf36_Half?
  I'm inclined not to change, but to allow indices in [SHN_HIRESERVE+1,PDP10_UINT18_MAX]
  as-is without going through SHN_XINDEX.

- Same question for PN_XNUM?

- Summarize the differences between Elf32 and Elf36 in a document somewhere.

pdp10-stdio:

- Handle non-seekable output files better (i.e., allow 8to9 to write to stdout)

Tools:

- size: implement it
- strip: implement it
- ld: implement it
- readelf: add support for relocs
- readelf: add support for program headers
- as:
  * add support for named sections
  * add support for sub-sections
  * add support for data directives (.word, .asciz, etc)
  * add support for relocs
  * add support for extended opcodes (emit second opcode after current .text section)
  * add support for symbolic references to 30 or 36-bit addresses via something like %hi/%lo functions