Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibC/sys/select.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <fd_set.h>
+#include <string.h>
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+__BEGIN_DECLS
+
+int select(int nfds, fd_set* readfds, fd_set* writefds, fd_set* exceptfds, struct timeval* timeout);
+
+__END_DECLS