FIXED: Raise-condition in maintaining thread_highest_id.  Could result in running threads considered non-existent.
FIXED: Raise-condition in maintaining thread_highest_id.  Could result in
running threads considered non-existent.

koryonik/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel