[3757cdf808] Refactoring seems to reduce (maybe somewhat kinda sorta) a 
bizarre performance regression.  Still not what it was.  Damn Heisenbugs.
Reduce the cost of Preserve/Release on channels
Complete transformation off Tcl_Preserve() legacy onto ref counting.
[3757cdf808] More clock refactoring with spooky impact on [string match]
performance.
merge trunk