more of -Wall fixes from Cristian Ionescu-Idbohrn.
Some are fixing real bugs.

function                                             old     new   delta
syslogd_main                                         938     958     +20
get_signum                                           136     143      +7
obj_load                                             777     782      +5
recv_from_to                                         210     214      +4
get_next_block                                      1795    1799      +4
display_topmem_process_list                         1117    1121      +4
logread_main                                         484     487      +3
buffer_fill_and_print                                 73      76      +3
kill_main                                            687     689      +2
ll_remember_index                                    240     241      +1
do_stats                                             452     453      +1
if_readconf                                          166     165      -1
display_process_list                                1192    1191      -1
run_applet_and_exit                                  507     505      -2
print_signames                                        33      31      -2
parse_one_line                                      1092    1090      -2
find_out_spec                                         57      55      -2
add_ksymoops_symbols                                 421     419      -2
ash_main                                            1407    1402      -5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 11/8 up/down: 54/-17)            Total: 37 bytes

diff --git a/loginutils/getty.c b/loginutils/getty.c
index da0dce3..5e16182 100644
--- a/loginutils/getty.c
+++ b/loginutils/getty.c
@@ -479,7 +479,7 @@
 			default:
 				if (!isascii(ascval) || !isprint(ascval)) {
 					/* ignore garbage characters */
-				} else if (bp - logname >= size_logname - 1) {
+				} else if ((int)(bp - logname) >= size_logname - 1) {
 					bb_error_msg_and_die("%s: input overrun", op->tty);
 				} else {
 					full_write(1, &c, 1); /* echo the character */