Verify that the AST contains at least 1 terminating paragraph

[c272]

Currently, with the introduction of paragraphs, the user can forgo entering a "STOP RUN" clause since the compiler currently has no ability to perform a walk of the call graph to determine whether the program will at some point (theoretically) enter a terminating block.

Perhaps a verify_ast function or something similar should be introduced to perform a static analysis pass before the code generation stage. Does not impact functionality, returns still work as expected, this is just not ideal from the user or compliance perspective.