TIP 429 Implementation: [string cat]
Don't use [pid] in tests, stick to constant literals.
Tidy up the docs
merge trunk
Hum. Really merge trunk.
More optimized non-BC [string cat] using Tcl_AppendObjToObj() - thx Donal
Add constant folding to [string cat]. Mixed-quote idiom is now compiled to a single push.
Better organize [string cat] by chunks of 255 args.
More aggressive constant folding in [string cat]. Thanks AndreasK for kicking.
Fix comment inaccuracy.
merge trunk
TIP 429 implementation.  New command [string cat].