Mark file for reuse.
 [rsc] --rw-rw-r-- M 1012724 glenda sys 575 Dec  9 10:43 sys/src/ape/lib/ap/stdio/sclose.c
	/n/sourcesdump/2005/1209/plan9/sys/src/ape/lib/ap/stdio/sclose.c:9,14 - 
	/n/sourcesdump/2005/1210/plan9/sys/src/ape/lib/ap/stdio/sclose.c:9,15
	  	default:	/* ERR CLOSED */
	  		if(f->buf && f->flags&BALLOC)
	  			free(f->buf);
	+ 		f->state=CLOSED;
	  		f->flags=0;
	  		return NULL;
	  	case OPEN: