Improve test suite.
Thanks to Leonard Crestez (Alioth: #311396, Debian: #511788).
`assert_complete' is improved. It proved difficult to tell tcl to ignore
backslash escapes, e.g. the `\b' is no BACKSPACE but a literal `b'. The added
function `split_words_bash' should to the trick now.
Added function `assert_no_complete' which can also be reached by calling
`assert_complete' with an empty `expected' argument:
assert_complete "" qwerty
d866854066