Fix errors in AVR tutorials

[aa-dit-yuh]

Bug report:

- ./_site/tutorial/avr/avrbasics/index.html
  *  External link https://lh6.googleusercontent.com/GFJw9DZjoXFRqEGM4a35CKFW1J9ojJy8bOUADuN9_oRj84sEn07LSgc4kgJjEJk8ZiAtvtxUMf1N-bkoo-W6OxGt7O6dZ4fSFS3EIgIUJ8K9iNlvQ1BMA0qn failed: 404 No error
  *  External link https://lh6.googleusercontent.com/ykB7vjDDgrv-8kayG6_r3-Zpnqc0apNcJppoCLLnOgvNxKlMB-BPDiXCi0sy11z44Jj4r9LK5XF2CJhBdH3dwLNhvwtbRqwdne7KYA0VMJ_4bnrBy0nl1dgVTQ failed: 404 No error
- ./_site/tutorial/avr/avrprog/index.html
  *  External link http://www.atmel.in/microsite/atmel_studio6 failed: got a time out (response code 0)
  *  External link https://lh3.googleusercontent.com/lV10-c6C702DXTabBO3dz8T16wWo7KaHvqajSPj2SMpMJArNN57u2T0BQFgr76-8NN6rDPxXUHX2F5KNiEJVTryK0Hn2kTjsTekGUYjHlV2Sk2MNlZ5IUObj failed: 404 No error
  *  External link https://lh3.googleusercontent.com/upitXdIaWxb_JVq4-93lEmpXy6Bs4u7-_QZk0qc96IqFK8aI_2hpRLl26-KwYKhH2uVJGUUCyFEKfSY4rs6tu-L_wu4U1_9d_qo2MOztf727tuS-k8i9TTR_ failed: 404 No error
  *  External link https://lh3.googleusercontent.com/zcyXSZXQ7JPaTO05C7aZA_Yh47YJ_fwLyV7UFFqQHSQYkfb897801V_40rqJpOKLeIpcJgHHoXbFt72-0-Hlj-qk4SrrBKGh9TrYvURwf-zzd8wRrUqH4qzr failed: 404 No error
  *  External link https://lh4.googleusercontent.com/r0Vv2nSfJV8T19f4QrkGkrVh6lB9Ng-MBRxrI-8wjlCS1wBAMVfgSJIeyyfTBCFlcEEO8LJ9Jg5cwZN1s-rywVDuSWwS47GuAdJVYkStf5r6C2mwoeJPtvof failed: 404 No error
  *  External link https://lh5.googleusercontent.com/Ur3c8TsmE5JfadDCX6XnQJ9ClxBmS2vM5DWuR8jDOfmEP0p5qPOZYNZIKdQM1oCCx1vc-P3w16bOE_Sf_h90VlfVTfak_oGqdXYqeznob33T-zfQ0UvyzWBO failed: 404 No error
  *  External link https://lh5.googleusercontent.com/YMlaxc0jGNODJGnmQ4RCbCe3vrf6s_dC6DgE2mID7gJJ22PdYFFGxiFRVh-0pDKh56qh0_0sW2q8JXyLg3vnulIEPTfFsM5P7jQKYxXKbCj9MWptvZHS3Ued failed: 404 No error
  *  External link https://lh6.googleusercontent.com/qf9mUAJt_-KMEqrIrP3yOJFF5u-9Pq9yyoULsS2PzrGqV0VtCP6A_CAo9OglqkDy9g5qyB0mePazBAOqH-xl7uTY7EuywbrrtTWnBWyLGWvssHYXaWgns2AJ failed: 404 No error
- ./_site/tutorial/avr/usart/index.html
  *  External link http://robotix.in/samplecode/bot_control.h failed: 404 No error
  *  External link http://robotix.in/samplecode/tserial.cpp failed: 404 No error
  *  External link http://robotix.in/samplecode/tserial.h failed: 404 No error
  *  External link https://docs.google.com/drawings/image?id=slvYquHXgUeM4iu0DpvfvgQ&w=610&h=162&rev=37&ac=1 failed: 410 No error
  *  External link https://lh3.googleusercontent.com/HQzmQjHO3DndpVzqQg89hUX0opwL0BEbIcdgEN3N0SrxzkAW57tDe5eZcvvIHmSfU3ETnTTSrbrvPMNSQ_qdCh5Ra4klcv7jzVMGS1OVKwrt3mULGVY failed: 404 No error
  *  External link https://lh4.googleusercontent.com/1hOAVMtlBCCCWV6x1Ew_ZKn9H_K1Z1OOKK_YufokmXQLHQ2VDFY_Fv6ztcBmkZEzNcLh-YrQg7BmInjl58EybrG81_f50fPXQFH-FsFF9X9BNrYyUbI failed: 404 No error
  *  External link https://lh4.googleusercontent.com/QFX0a7LtoebctZ__9JGofxk6d1ZWVkVd1A0BwRz6Kh34y56uDpI6EWEZk8VKnekIiKXIQS-lkz3L2dPGJFkNWcBd4eB8A7UeStQb7onw0A3y-oz7xh8 failed: 404 No error
  *  External link https://lh4.googleusercontent.com/ycy-4nB7P8hulU9kHrA5AAp1E3hShatCMKRDso2mVhrQGb9wvrfC9ivPdBiSYyGhmhS_UvmFdcChQ6jZ09TgepTPlHtwOUcGouKW-I5gMrYs2IQZBeY failed: 404 No error