Mistyped features in feature-expressions evaluate as true

[npetryk]

com.rmn.version-qualified.qualifiers.feature/eval-feature-expr walks a feature expression and replaces features with true or false, then evals the expression. If a (for example) keyword is found in the expression which is not a known-feature?, it will not be replaced. The effect of this is that when evaling the expression, the keyword will basically evaluate as true in boolean logic expressions.

In this case, we should probably warn the user that we found a keyword but it was not a known feature, or just error out completely. The latter would cause problems if they legitimately wanted to put a keyword in the expression but did not mean it to refer to a version.

We should be cognizant that not all feature names are keywords

Example expression

(and :feature1 (not :faeture2))

Assuming that :faeture2 is a typo of :feature2, this will expression will always be false because we compile it to

(and true (not :faeture2))

rather than

(and true (not false))

[npetryk]

In these expressions, it may be safe to assume that the first form in a list is always some boolean operator, and the rest of the non-list forms refer to versions -- this could be keywords, symbols, strings, etc..

Perhaps we should assert that non-list, non-first-element-of-a-list forms are all known-feature? by default, and then allow the user to add metadata to the feature-expression to turn off this check.

^:com.rmn.version-qualified.qualifiers.feature/skip-known-feature-check
(and :feature1 (not :faeture2))