Optimizations and general bytecode generation improvements.
Partial fix: still ongoing
Fix implementation of INST_LIST_EXPANDED.
Corrected the stack balancing in the special [list {*} ] compiler.
Optimizations and general bytecode generation improvements.
Upgrade to zlib 1.2.8
compiler warning
merge trunk. 
Add back Tcl_AddErrorInfo to stub table (it's still used by Tk 8.6)