Add VS2012 update 3 version number.
Remove the VS2012 update 2 workaround now that update 3 is out.

This reverts da78edb, 8d50410 and 0d6bec3
Audio Switcher: Fix custom channel mapping after 14bc5b28faaf7fe59c9a52d73c237ea47402e8c6.

The output was silent when custom channel mapping was enabled.

This commit fixes #3257.