resolve symbol role conflict

[athos]

imported from athos/genuine-highlighter#6

Each symbol has roles among special, macro, var, local or symbol (for now). And we now temporarily assume that every symbol has only a single role.
Taking into account more complicated situations (e.g. where a symbol would be put into multiple places through macro expansion), we should allow symbols to take more than a role. To this end, the extractor must be equipped with a kind of conflict resolusion mechanism.

[athos]

Recently, we noticed we don't need to resolve symbol conflict at all at the analyzer level. In fact, users might want to know all of the possible symbol roles in some cases.

So, we concluded what we need to do is to collect possible symbol roles and annotate them to the symbol.