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/act.informative.c

@@ -2593,7 +2593,7 @@ distance, int door)
     if (!*buf)
       sprintf(buf, "You see %s", GET_NAME(i));
     else
-      sprintf(buf, "%s%s", buf, GET_NAME(i));
+      strcat(buf, GET_NAME(i));
     if (--count > 1)
       strcat(buf, ", ");
     else if (count == 1)

src/dg_olc.c

@@ -476,7 +476,8 @@ static void script_syntax_highlighting(struct descriptor_data *d, char *string)
             }
         }
 
-        sprintf(buffer, "%s%s\tn\r\n", buffer, line);
+        strcat(buffer, line);
+        strcat(buffer, "\tn\r\n");
     }
     
     page_string(d, buffer, TRUE);

src/improved-edit.c

@@ -358,7 +358,9 @@ void parse_edit_action(int command, char *string, struct descriptor_data *d)
 	s++;
 	temp = *s;
 	*s = '\0';
-	sprintf(buf, "%s%4d: ", buf, (i - 1));
+	char buf3[8];
+	sprintf(buf3, "%4d: ", (i - 1));
+	strcat(buf, buf3);
 	strcat(buf, t);
 	*s = temp;
 	t = s;

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;
         }