add minilibc files for gcc compiler

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@377 bbd45198-f89e-11dd-88c7-29a3b14d5316

libc/minilibc/math.c

+#include <math.h>
+
+/* Fix me */
+double sin(double x) 
+{
+	#warning sin function not supported for this platform
+}
+
+double cos(double x) 
+{
+	#warning cos function not supported for this platform
+}

libc/minilibc/math.h

+#ifndef __STDIO_H__
+#define __STDIO_H__
+
+#endif

libc/minilibc/stdio.h

+#ifndef __STDIO_H__
+#define __STDIO_H__
+
+#endif
+