Resolve Wrestrict warnings on GCC 8.1.1 (#51)

* Fix several misleading indentation warnings on GCC 8.1.1

* Fix reliance on undefined strcpy/sprintf behavior (-Wrestrict warnings)

The standard states that strcpy results in undefined behavior when the source
and destination buffers overlap. I resolved this with a combination of memmove
and strlen. Note that the resulting code is slightly less efficient.

Similarly, sprintf's behavior is undefined when copying takes place between
objects that overlap. I replaced most of these with a simple strcat, though
one required a temp buffer.

* Fix format in improved-edit.c to match surrounding code

src/shop.c

@@ -1101,7 +1101,7 @@ static int read_type_list(FILE *shop_f, struct shop_buy_data *list,
       for (tindex = 0; *item_types[tindex] != '\n'; tindex++)
         if (!strn_cmp(item_types[tindex], buf, strlen(item_types[tindex]))) {
           num = tindex;
-          strcpy(buf, buf + strlen(item_types[tindex]));	/* strcpy: OK (always smaller) */
+          memmove(buf, buf + strlen(item_types[tindex]), strlen(buf) - strlen(item_types[tindex]) + 1);
           break;
         }