Replace std::mins/max with clamp function (#2062)

Adding a clamp function makes some of these range limitations a bit prettier and removes some #include's.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 28117 W: 6300 L: 6191 D: 15626
http://tests.stockfishchess.org/tests/view/5c9aa1df0ebc5925cfff8fcc

Non functional change.

src/search.cpp

@@ -18,7 +18,6 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <algorithm>
 #include <cassert>
 #include <cmath>
 #include <cstring>   // For std::memset
@@ -461,7 +460,7 @@ void Thread::search() {
           && !mainThread->stopOnPonderhit)
       {
           double fallingEval = (306 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
-          fallingEval        = std::max(0.5, std::min(1.5, fallingEval));
+          fallingEval = clamp(fallingEval, 0.5, 1.5);
 
           // If the bestMove is stable over several iterations, reduce time accordingly
           timeReduction = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0;