Style: Replace header guards with #pragma once

core/math/math_defs.h

@@ -28,8 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#ifndef MATH_DEFS_H
-#define MATH_DEFS_H
+#pragma once
 
 #define CMP_EPSILON 0.00001
 #define CMP_EPSILON2 (CMP_EPSILON * CMP_EPSILON)
@@ -136,5 +135,3 @@ typedef double real_t;
 #else
 typedef float real_t;
 #endif
-
-#endif // MATH_DEFS_H