Fix issue with radio buttons and numeric correct answers.

[dpvc]

Fix issue with radio buttons not giving an error if the index is out of range, and add noindex option to prevent numeric value from being used as an index.

http://bugs.webwork.maa.org/show_bug.cgi?id=3718

includes one example of this. You can also test it by using

loadMacros("parserRadioButtons.pl");
TEXT(RadioButtons([1,2,3],2)->{data}[0],",");
TEXT(RadioButtons([1,2,3],2,noindex=>1)->{data}[0]);

This should give you B2,B1 as the result after the patch (before it should be B2,B2).

Also

loadMacros("parserRadioButtons.pl");
TEXT(RadioButtons([1,2,3],5));

should produce an error about the correct answer index being outside the range of choices. (Before the patch, it produces a warning about $value not being defined).

[goehle]

Fixes work as advertised.