bistromathic: beware of portability issues with readline
In some cases readline emits a trailing spaces after the last
suggestion, which results in errors such as:
```
-( - atan cos exp ln number sin sqrt$
+( - atan cos exp ln number sin sqrt $
```
Reported by Christopher Nielsen <mascguy@github.com>.
<https://trac.macports.org/ticket/59927#comment:48>
<https://trac.macports.org/attachment/ticket/59927/bison-3.7.6-test-10.13.test-suite.log>
* examples/test (run): Add support for -t.
* examples/c/bistromathic/bistromathic.test: Use it.