Don't set dirty all lines because tswapcreen do it

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>

st.c

@@ -2700,14 +2700,12 @@ tresize(int col, int row) {
 
 	/* resize each row to new width, zero-pad if needed */
 	for(i = 0; i < minrow; i++) {
-		term.dirty[i] = 1;
 		term.line[i] = xrealloc(term.line[i], col * sizeof(Glyph));
 		term.alt[i]  = xrealloc(term.alt[i],  col * sizeof(Glyph));
 	}
 
 	/* allocate any new rows */
 	for(/* i == minrow */; i < row; i++) {
-		term.dirty[i] = 1;
 		term.line[i] = xmalloc(col * sizeof(Glyph));
 		term.alt[i] = xmalloc(col * sizeof(Glyph));
 	}
@@ -2727,7 +2725,7 @@ tresize(int col, int row) {
 	tsetscroll(0, row-1);
 	/* make use of the LIMIT in tmoveto */
 	tmoveto(term.c.x, term.c.y);
-	/* Clearing both screens */
+	/* Clearing both screens (it makes dirty all lines) */
 	orig = term.line;
 	c = term.c;
 	do {