implement the adjtime and adjtimex functions (nonstandard)

src/linux/adjtimex.c

@@ -0,0 +1,7 @@
+#include <sys/timex.h>
+#include "syscall.h"
+
+int adjtimex(struct timex *tx)
+{
+	return syscall(SYS_adjtimex, tx);
+}