fix some gcc warnings (#73) * tweak string size fix gcc8 warnings ``` svr-agentfwd.c: In function 'bindagent': svr-agentfwd.c:254:53: warning: '%s' directive output may be truncated writing up to 107 bytes into a region of size between 0 and 107 [-Wformat-truncation=] snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", path, sockfile); ^~ ~~~~~~~~ svr-agentfwd.c:254:2: note: 'snprintf' output between 2 and 216 bytes into a destination of size 108 snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", path, sockfile); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` * cleanup signed/unsigned comparison fix gcc8 warnings ``` scp.c: In function 'do_local_cmd': scp.c:132:17: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] for (i = 0; i < a->num; i++) ^ scpmisc.c: In function 'addargs': scpmisc.c:161:25: warning: comparison of integer expressions of different signedness: 'int' and 'u_int' {aka 'unsigned int'} [-Wsign-compare] } else if (args->num+2 >= nalloc) ^~ scpmisc.c: In function 'replacearg': scpmisc.c:183:12: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] if (which >= args->num) ^~ scpmisc.c: In function 'freeargs': scpmisc.c:196:17: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] for (i = 0; i < args->num; i++) ^ ``` see https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/misc.h.diff?r1=1.16&r2=1.17

#include "includes.h"
#include "dbutil.h"
#include "list.h"

void list_append(m_list *list, void *item) {
	m_list_elem *elem;
	
	elem = m_malloc(sizeof(*elem));
	elem->item = item;
	elem->list = list;
	elem->next = NULL;
	if (!list->first) {
		list->first = elem;
		elem->prev = NULL;
	} else {
		elem->prev = list->last;
		list->last->next = elem;
	}
	list->last = elem;
}

m_list * list_new() {
	m_list *ret = m_malloc(sizeof(m_list));
	ret->first = ret->last = NULL;
	return ret;
}

void * list_remove(m_list_elem *elem) {
	void *item = elem->item;
	m_list *list = elem->list;
	if (list->first == elem)
	{
		list->first = elem->next;
	}
	if (list->last == elem)
	{
		list->last = elem->prev;
	}
	if (elem->prev)
	{
		elem->prev->next = elem->next;
	}
	if (elem->next)
	{
		elem->next->prev = elem->prev;
	}
	m_free(elem);
	return item;
}