make images more responsive in HTML pages

We add the following default IOCCC setting to `ioccc.css`:

```css
img {
    height: auto;
    max-width: 95%;
    position: relative;
}
```

We also modified `ioccc.css` to use consitent 4 space indentation.
No other `ioccc.css` changes were made.

ioccc.css

@@ -443,6 +443,12 @@ a:active {
     color: red;
 }
 
+img {
+    height: auto;
+    max-width: 95%;
+    position: relative;
+}
+
 /* IOCCC classes ================================================================================= */
 
 /* Left - class for placing things on the left side */