BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/include/sys/cdefs.h

@@ -0,0 +1,14 @@
+#ifndef _SYS_CDEFS_H
+#define _SYS_CDEFS_H 1
+
+#define __banan_libc 1
+
+#ifdef __cplusplus
+	#define __BEGIN_DECLS extern "C" {
+	#define __END_DECLS }
+#else
+	#define __BEGIN_DECLS
+	#define __END_DECLS
+#endif
+
+#endif