Add test for parsing case statements.

This completes conditional statement/expression parser tests.
Add test for calls.

This modifies the factory to produce a FQN instead of a LiteralString
for the Functor when using CALL_NAMED_FUNCTION.

This commit also corrects the grammar (it passed the token, not the
text as the function name).

The output for a call is (invoke name ...) for a procedure call, and
(call name ...) for a function call (that should/may produce rvalue).