Kernel/LibC: Implement fchmod

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

@@ -55,6 +55,7 @@ __BEGIN_DECLS
 	O(SYS_TTY_CTRL,			tty_ctrl)		\
 	O(SYS_POWEROFF,			poweroff)		\
 	O(SYS_CHMOD,			chmod)			\
+	O(SYS_FCHMOD,			fchmod)			\
 	O(SYS_CREATE,			create)			\
 	O(SYS_CREATE_DIR,		create_dir)		\
 	O(SYS_UNLINK,			unlink) 		\