tools/listsym: `unknown` functions when multiple symbols at same address

[MonsterDruide1]

If multiple function symbols are defined to point ot the same address, the function CSV can only map one of those to the correct address - because currently, no duplicate entries are contained.

I am not sure if duplicate entries are even allowed there, or if that causes other problems with tools/check or similar. If that's the case, a different solution has to be found - if the function map ever makes it into the repo, that one could also be used to map between duplicate symbols.

[Fuzzy2319]

I tested to duplicate an entry, it doesn't work.

[LynxDev2]

This should be fixed now since multiple symbol support is one of the features of the new file list format and missing symbols for ctors and dtors have been added (which were the ones listsym was complaining about)

[MonsterDruide1]

Yes - fixed in #633, closing.