versioner: assorted fixes.

Zero initialize the contents of ArchMap, keep track of the symbol name
in Declaration, remove unnecessary copies in loops.

Change-Id: I47b07755846f252b83ffc4c89547a34b2f7ab868
diff --git a/tools/versioner/src/DeclarationDatabase.h b/tools/versioner/src/DeclarationDatabase.h
index ac5de27..bba826d 100644
--- a/tools/versioner/src/DeclarationDatabase.h
+++ b/tools/versioner/src/DeclarationDatabase.h
@@ -92,7 +92,7 @@
       return false;
     }
 
-    for (auto it : arch_availability) {
+    for (const auto& it : arch_availability) {
       if (!it.second.empty()) {
         return false;
       }
@@ -142,6 +142,7 @@
 std::string to_string(const Location& loc);
 
 struct Declaration {
+  std::string name;
   Location location;
 
   bool is_extern;