minor compiler warning fixes and coding style

src/core/dns.c

@@ -475,7 +475,7 @@ static void
 dns_init_local(void)
 {
 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
-  int i;
+  size_t i;
   struct local_hostlist_entry *entry;
   /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
   struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;

src/core/ipv4/autoip.c

@@ -456,6 +456,10 @@ autoip_tmr(void)
             }
           }
           break;
+
+        default:
+          /* nothing to do in other states */
+          break;
       }
     }
     /* proceed to next network interface */

src/core/ipv4/ip_frag.c

@@ -769,7 +769,7 @@ ip4_frag(struct pbuf *p, struct netif *netif, const ip4_addr_t *dest)
     }
     /* fill in the IP header */
     SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN);
-    iphdr = rambuf->payload;
+    iphdr = (struct ip_hdr*)rambuf->payload;
 #else /* LWIP_NETIF_TX_SINGLE_PBUF */
     /* When not using a static buffer, create a chain of pbufs.
      * The first will be a PBUF_RAM holding the link and IP header.

src/core/stats.c

@@ -124,7 +124,7 @@ stats_display_mem(struct stats_mem *mem, const char *name)
 void
 stats_display_memp(struct stats_mem *mem, int index)
 {
-  char * memp_names[] = {
+  const char * memp_names[] = {
 #define LWIP_MEMPOOL(name,num,size,desc) desc,
 #include "lwip/memp_std.h"
   };