General cleanup

Simplifies logic in a couple places and removes a redundant function
call.

Signed-off-by: Devin J. Pohly <djpohly@gmail.com>

st.c

@@ -1693,7 +1693,6 @@ csihandle(void)
 		tputtab(csiescseq.arg[0]);
 		break;
 	case 'J': /* ED -- Clear screen */
-		selclear();
 		switch (csiescseq.arg[0]) {
 		case 0: /* below */
 			tclearregion(term.c.x, term.c.y, term.col-1, term.c.y);