Remove AddType mappings covered by Apache v2.2.0+

Remove filename extension to content type mappings that are already
provided by Apache v2.2.0+:

+---------------------------------+-------------+---------------------+
|         MIME Type               |   Filename  |    Apache version   |
|                                 |  extension  |   since introduced  |
+---------------------------------+-------------+---------------------+
| application/x-shockwave-flash   |      swf    |      < v2.0.x       |
| image/svg+xml                   |      svg    |        v2.0.x       |
| image/x-icon                    |      ico    |        v2.0.x       |
+---------------------------------+-----------------------------------+

Close #4.