[clang] [clang][Tooling] Reuse standard-library symbol descriptors (PR #202663)

[David Zbarsky via cfe-commits]

================
@@ -24,6 +24,12 @@ namespace {
 // Symbol name -> Symbol::ID, within a namespace.
 using NSSymbolMap = llvm::DenseMap<llvm::StringRef, unsigned>;
 
+struct SymbolMapping {
+  const char *QName;
+  unsigned NSLen;
+  const char *HeaderName;
+};
----------------
dzbarsky wrote:

@aengelke I think we can just use 2 llvm::StringTable here, that should also avoid the relocations. WDYT?

https://github.com/llvm/llvm-project/pull/202663