Cmdln

- Some Python 2.6-ification. No functional change.

- Issue 1: fix readline-based completion and history (from Joshua
Gallagher).
- Experimental automatic bash completion support. See r8 for details:
svn diff -r7:8 http://cmdln.googlecode.com/svn/trunk/cmdln.py
- Some minor improvements to line2argv processing (r7).
- Fix "${help_list}" layout problems and more closely follow optparse
option list help output (r4).
- Moved project to Google Code (http://code.google.com/p/cmdln)
for Subversion there and for the issue tracker.

- Experimental Bash completion integration. See "bash completion support"
section in cmdln.py for details.

- [backward incompat] `Cmdln.main()` no longer takes an `optparser`
argument. Top-level option parsing has been changed so that top-level
options for a `Cmdln` subclass can more naturally be defined and
handled on the class definition. Changes:
- `Cmdln.main()` calls `self.get_optparser` to get an option handler.
Subclasses should overload this method for custom top-level options.
- After option parsing, but before sub-command handling, the
`self.postoptparse()` hook is called.
- Add a `version` attribute on `Cmdln` subclasses. If set, the default
top-level option parser will have a `--version` attribute.
- [backward incompat] Simplify the StopProcessing/opts.stop handling for
option handling in subcommands. The "opts" argument to "do_*"
sub-command functions will no longer have a "stop" value.
StopProcessing is now called StopOptionProcessing. This shouldn't
affect simple usage of cmdln.py.

- Fix a bug where errors with passing an incorrect number of args to
functions in do_foo() implementations would be masked.

- Remove the implicit prefixing of a command's help string with
"${cmd_name}: ". This can be surprising for the case of a "help_FOO"
function without an associated "cmd_FOO" function.