core: Resolve misc cases of variable shadowing

Resolves shadowing warnings that aren't in a particularly large
subsection of core. Brings us closer to turning -Wshadow into an error.

All that remains now is for cases in the kernel (left untouched for now
since a big change by bunnei is pending), and a few left over in the
service code (will be tackled next).

src/core/core_timing.h

@@ -102,7 +102,7 @@ public:
     /// We only permit one event of each type in the queue at a time.
     void RemoveEvent(const std::shared_ptr<EventType>& event_type);
 
-    void AddTicks(u64 ticks);
+    void AddTicks(u64 ticks_to_add);
 
     void ResetTicks();