Information about aliases in llvm-nm, and aliases ignored in llvm-extract.

I was wondering if there would be any objection to adding a flag to llvm-nm to either mark a symbol in a special way if it is an alias (suggestions welcome), or a flag to skip aliases completely. This could be a hidden flag if it is something we don’t want to expose.

I would also like to change llvm-extract (ExtractGV) to eliminate any aliases that do not have a matching aliasee for the values to extract. Currently llvm-extract keep all aliases. Alias names it could perhaps be matched with a -alias flag like the -func flag, but unless someone else needs it I will probably not implement it.