Remove an unnecessary mutex.

When ++seqno is incremented in export_commit, it's never done from threads.
The parallelized part of the processing is long dome by then.
All regression tests pass.
Cosmetic fixes.
Avoid expensive calls to expandline(). All regression tests pass.
Rename a function for clarity.
Don't do unnecessarymutex calls when threads < 2.

All regression tests pass.
Cosmetic fix.
Use a lockless increment instead of a mutex, if possible.
We finally seem to have scheduler signaling that works.
More timing data.
Head off some potential screwage by being strict about volatile declarations.

All regression tests pass.
Globals lurk everywhere!  Stamping out another two.

All regression tests pass.
Discard load_status(). A running percentag is more usel than an animation.
Remove an obsolete option.
Clean up the grammar by removing an unused terminal.
Eliminate grammar conflicts, hoping for faster parsing.
Reliably clean up lex.h.