Remove remnants of tagged booleans.

Booleans don't get a tag bit anymore (values with a tag bits value
of 3 are now Unicode characters, not booleans).
Merge pull request #461 from waywardmonkeys/remove-boolean-tag-remnants

Remove remnants of tagged booleans.
[rt] Mark branch in profiling as unlikely.
Fix a couple of typos in comments.
Add note about new list of projects.
Fix typo.
Typo fixes.
[dfmc] Clean up #"default-open" code.

This code has been disabled since 1999 (it couldn't happen then).
Also, remove current-compilation-mode() as it is no longer used
now that this is gone.
Merge pull request #464 from waywardmonkeys/cleanup-default-open

[dfmc] Clean up #"default-open" code.
Fix typo.