Draft fix for Bug 0b874c344d.  Includes test.
Simplify the coding of the unchain operation.
Improve descriptions of character escapes and ranges in Tcl.n.
Improve output format handlers to cope with added escape for en-dashes.
Refactoring work on the "chain" operation.
Factor out the level offsetting into a final pass.  Let the first
pass of the "chain" operation just stitch things together and count levels.
Making the optimizer pluggable by extensions; please review for committing to trunk
Making the optimizer pluggable by extensions
Big simplification of the bug fix.
merge trunk
[0b874c344d] Fix for nested coroutines ability to stitch together multiple
parts of the CmdFrame chain traversed by [info frame].
Add TclRegisterLiteral() to internal stub table (from "mig-optimize" branch, looks like a good idea anyway)
remove INST_TRY_CVT_TO_NUMERIC when it is known not be necessary (cherrypick from mig-optimize)
fix stack counting bug in new catch compiler, commit 62a51cdb45.
remove duplicate statement in previous commit
remove unnecessary messing around INST_CONTINUE and INST_BREAK: local continue/break are already converted to jumps, so that these are either caught or returned - in either case, the stacks are cleaned up properly by TEBC itself.
Added new tools for managing and verifying the stack depth during compilation. Used it in some spots in the compiler and in TclCompileCatchCommand.
merge trunk