Use C++ headers instead of C headers (#1179)

Remove some unnecessary includes.

Signed-off-by: Marco Antognini <marco.antognini@arm.com>

test_conformance/math_brute_force/binary_double.cpp

@@ -18,7 +18,7 @@
 #include "test_functions.h"
 #include "utility.h"
 
-#include <string.h>
+#include <cstring>
 
 const double twoToMinus1022 = MAKE_HEX_DOUBLE(0x1p-1022, 1, -1022);