git branch cleanup -- please check!!!

[Alvin Wong]

Hi Boud,

All of my branches were either merged or obsolete, so they can be removed.

>   origin/alvin/T6503-python-win
>   origin/alvin/T6503-winpython-temp
>   origin/alvin/T6521-deps-update-win
>   origin/alvin/T6696-opengl-angle
>   origin/alvin/T6760-angle-test-1
>   origin/alvin/T6976-angle-3.3
>   origin/alvin/T7198-win-build-scripts

Best Regards,

Alvin