[llvm] Add symbol version support to llvm-ifs (PR #163030)

[Saleem Abdulrasool via llvm-commits]

================
@@ -62,6 +64,36 @@ struct IFSSymbol {
   bool operator<(const IFSSymbol &RHS) const { return Name < RHS.Name; }
 };
 
+struct IFSVerDef {
+  std::string Name;
+  std::vector<std::string> Parents;
+};
+
+inline bool operator==(const IFSVerDef &Lhs, const IFSVerDef &Rhs) {
+  if (Lhs.Name != Rhs.Name || Lhs.Parents != Rhs.Parents)
----------------
compnerd wrote:

It might be a bit easier to read inverted:

```
if (lhs.Name == rhs.Name && lhs.Parent == rhs.Parents)
  return true;
return false;
```

https://github.com/llvm/llvm-project/pull/163030