Corrected some GCC 7.1+ compile warnings (#3522)

* Fixes #2787 and fixes #3513.
* Resolved some format-truncation warnings.
* The remaining will be fixed at a later time.
Thanks to @RadianFord and @Lemongrass3110!

src/map/npc_chat.cpp

@@ -372,7 +372,7 @@ int npc_chat_sub(struct block_list* bl, va_list ap)
 				// save out the matched strings
 				for (i = 0; i < r; i++)
 				{
-					char var[6], val[255];
+					char var[255], val[255];
 					snprintf(var, sizeof(var), "$@p%i$", i);
 					pcre_copy_substring(msg, offsets, r, i, val, sizeof(val));
 					set_var(sd, var, val);