Locking of mutexes while threads disabled.
Imported from https://youtrack.roxen.com/issue/PIKE-62
Reported by @grubba
Blocked by PIKE-78
Attempting to lock mutexes (like lock_compiler()) ought to throw errors when threads are disabled.
Imported from https://youtrack.roxen.com/issue/PIKE-62
Reported by @grubba
Blocked by PIKE-78
Attempting to lock mutexes (like lock_compiler()) ought to throw errors when threads are disabled.