At least in neovim, `│vi:` is not recognized as a modeline because it
has no preceding whitespace. After fixing this, opening a file yields
an error because `net` is not an option. (`noet`, however, is.)
- Improve compatibility with Blink virtual machine
- Add non-POSIX APIs for joining threads and signal masks
- Never ever use anything except 32-bit integers for atomics
- Add some `#undef` statements to workaround `ctags` problems
This change includes a fix to Fetch() where an out of bounds memory read
could happen, when the reverse proxied endpoint omits the content-length
header. This caused a bunch of NUL chars to appear on TurfWar's /statusz
since it wouldn't actually overrun the buffer, and if it did it would've
been caught by MODE=asan builds.
