patch to remove redundant assignments

See:

https://github.com/xiph/theora/pull/13

This has been carried by vcpkg for quite a long time, as the library cannot be built with MSVC otherwise.

mentioned in commit 0d1edad2

mentioned in merge request !25 (merged)

mentioned in commit 291d154b

mentioned in commit 2c3c5992

mentioned in commit 3b5aee3f

closed with commit 3b5aee3f