Eat up "CSI 58" sequences

This is used in the wild by systemd systemctl for example and st
misinterpreted it as "blink", because it didn't know "58", then saw "5"
as "blink", and then didn't know "245".

This should print "foo" as normal text:

    printf '\e[58:5:245mfoo\n'
    printf '\e[58:2:50💯200mfoo\n'

Ref.
https://git.suckless.org/st/commit/f114bcedd113017d907aad32031db92c050f4bf3.html

st.c

@@ -1864,6 +1864,13 @@ tsetattr(const int *attr, int l)
 			term.c.attr.ucolor[2] = -1;
 			term.c.attr.mode ^= ATTR_DIRTYUNDERLINE;
 			break;
+		#else
+		case 58:
+			/* This starts a sequence to change the color of
+			 * "underline" pixels. We don't support that and
+			 * instead eat up a following "5;n" or "2;r;g;b". */
+			tdefcolor(attr, &i, l);
+			break;
 		#endif // UNDERCURL_PATCH
 		default:
 			if (BETWEEN(attr[i], 30, 37)) {