64-bit Vere

[ghost]

This PR introduces 64-bit Vere. The principle changes involved have to do with the introduction of a new type, c3_n, which is 32 bit or 64 bit depending on if it was compiled with -DVERE64.

The following work still needs to be done:

• every appearance of _tmp in pkg/noun (~800 locations)
• look at diff of pre and post VERE64 compilation with -Wconversion flag. Investigate every instance.
• run with llvm addr sanitizer, ubsan
  • found issues with asan and ubsan as of 61fc9de (lmdb addressed in vere: fix some undefined behavior #820)
• audit every jet
• migrations: bidirectional (use MSB of version tag to mark if vere64 or not? maybe also add metadata for pointer compression)
• integrate Joe's page based allocator
• new rsignal_setjmp/longjmp may have volatility problems (talk to Joe. maybe use atomics?)
• pkg/vere/noun-tests is completely broken
• every appearance of _tmp in any other subdirectory (~1000 locations)
• c3_w_clz, ctz, pc occurrences (we should change current occurrences to _tmp as we did with u3r_word, etc and go through them
• c3_etch_word, c3_sift_word occurrences (also change to _tmp)
• make sure everything works (C tests and hoon tests included) still for vere32
• PMA integration (easy in vere64, vere32 requires more involved work)
• revendor murmur3 with a size_t len
  • hoon: murmur3 revendor urbit#7186
  • mug: revendor murmur3 #840
  • target develop for mug: revendor murmur3 #840, do it in 2 commits (original vendor, our changes), include upstream commit hash in commit message
• test really big nouns in ames/fine/mesa
• the event log and other lmdb state should not need migration. we should double check events.c, disk.c
• there's a lot of bloq size related things in the jets that could be changed to greater than 32 for the 32 bit case

I will make this more granular and regularly update this as involved collaborators complete things.

[barter-simsum]

majority of changes in hashtable and trace. misc changes elsewhere. majority of remaining _tmp usage to convert to 32/64-bit limited to jets

[barter-simsum]

recommend concurrent or after completion of _tmp conversions to run zig build with -Wconversion clang opt. There are likely many violations prior to VERE64, so compare the diff between output before/after VERE64 changes and inspect those specific occurences

[matthew-levan]

Closing in favor of #715.