sincos, sincof, sincosl declarations in gnu/math.h

Signed-off-by: Zoltán Mizsei <zmizsei@extrowerk.com>

Change-Id: I44b39e8d76dd970e18e285b5d8b9bad715608154
Reviewed-on: https://review.haiku-os.org/715
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

headers/compatibility/gnu/math.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2018 Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _GNU_MATH_H_
+#define _GNU_MATH_H_
+
+
+#include_next <math.h>
+
+
+#ifdef _GNU_SOURCE
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void sincos(double x, double *sin, double *cos);
+extern void sincosf(float x, float *sin, float *cos);
+extern void sincosl(long double x, long double *sin, long double *cos);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif
+
+
+#endif	/* _GNU_MATH_H_ */