#164 allow functions to have zero or more values

[Danny Haynes]

Based on community discussion, there are some cases where it may be appropriate for functions to have 0 or more values (e.g. the count function should evaluate to 0 if it references something with no values). During the 5.11 release, we need to determine in which cases this behavior is appropriate and update the OVAL Interpreter accordingly. Attached is a patch that makes some of these changes. However, their integration into the OVAL Interpreter is pending the community discussion around this issue. This issue was originally brought up in the following oval-discussion-list post.

http://making-security-measurable.1364806.n2.nabble.com/count-function-against-component-evaluating-to-zero-values-tp7304434p7304434.html

[Danny Haynes]