Cycles: use std::min and max for extra overloads

intern/cycles/util/util_math.h

@@ -24,6 +24,7 @@
 
 #ifndef __KERNEL_GPU__
 #  include <cmath>
+#  include <algorithm>
 #endif
 
 
@@ -130,6 +131,9 @@ ccl_device_inline double min(double a, double b)
 	return (a < b)? a: b;
 }
 
+using std::min;
+using std::max;
+
 /* These 2 guys are templated for usage with registers data.
  *
  * NOTE: Since this is CPU-only functions it is ok to use references here.