Mark pointer arguments that cannot ever be null as [static 1].

Also constify some cases, too.

src/ndhc.c

@@ -96,7 +96,7 @@ struct client_config_t client_config = {
     .foreground = 1,
 };
 
-void set_client_addr(const char *v) { cs.clientAddr = inet_addr(v); }
+void set_client_addr(const char v[static 1]) { cs.clientAddr = inet_addr(v); }
 
 void print_version(void)
 {
@@ -212,7 +212,7 @@ static void signal_dispatch(void)
     }
 }
 
-static int is_string_hwaddr(char *str, size_t slen)
+static int is_string_hwaddr(const char str[static 1], size_t slen)
 {
     if (slen == 17 && str[2] == ':' && str[5] == ':' && str[8] == ':' &&
         str[11] == ':' && str[14] == ':' &&
@@ -225,7 +225,7 @@ static int is_string_hwaddr(char *str, size_t slen)
     return 0;
 }
 
-int get_clientid_string(char *str, size_t slen)
+int get_clientid_string(const char str[static 1], size_t slen)
 {
     if (!slen)
         return -1;