[Warnings] Fixed Const Reference

When a class returns a reference to a dereferenced pointer, if the
pointer does not point to a const object, returning that pointer as a
const has no effect. This was causing warnings.

To fix this, we want a refernece to a const object not a const reference
to an object (silly, I know). So we need to make this more clear in the
class.

libs/EXTERNAL/libtatum/libtatum/tatum/tags/TimingTags.hpp

@@ -113,6 +113,7 @@ class TimingTags {
                 using value_type = T;
                 using pointer = T*;
                 using reference = T&;
+                using const_reference = const T&;
 
                 Iterator(): p_(nullptr) {}
                 Iterator(pointer p): p_(p) {}
@@ -123,7 +124,7 @@ class TimingTags {
                 friend bool operator!=(Iterator a, Iterator b) { return a.p_ != b.p_; }
 
                 reference operator*() { return *p_; }
-                const reference operator*() const { return *p_; } //Required for MSVC (gcc/clang are fine with only the non-cost version)
+                const_reference operator*() const { return *p_; } //Required for MSVC (gcc/clang are fine with only the non-cost version)
                 pointer operator->() { return p_; }
                 reference operator[](size_t n) { return *(p_ + n); }