math_util: Remove the Clamp() function

C++17 adds clamp() to the standard library, so we can remove ours in
favor of it.

src/common/math_util.h

@@ -17,11 +17,6 @@ inline bool IntervalsIntersect(unsigned start0, unsigned length0, unsigned start
     return (std::max(start0, start1) < std::min(start0 + length0, start1 + length1));
 }
 
-template <typename T>
-inline T Clamp(const T val, const T& min, const T& max) {
-    return std::max(min, std::min(max, val));
-}
-
 template <class T>
 struct Rectangle {
     T left;