Fix STL Algorithm Header Errors When Included with Platform.h

"clamp" macro of Platform.h conflicts with "std::clamp" of the STL algorithm header. So `#include <algorithm>` forces Platform.h included after itself. This commit fixes the issue

common/Platform.h

@@ -77,4 +77,8 @@ using qboolean = int;
 #define V_min(a, b) (((a) < (b)) ? (a) : (b))
 #define V_max(a, b) (((a) > (b)) ? (a) : (b))
 
+#ifndef _ALGORITHM_
 #define clamp(val, min, max) (((val) > (max)) ? (max) : (((val) < (min)) ? (min) : (val)))
+#endif // _ALGORITHM_
+
+