Add support for Win64 exception handling in x86 asm
The x64 assembly code does not comply with Windows x64's ABI. Specifically, any function that modifies the stack pointer or any nonvolatile register must have metadata in the executable that describes the stack frame.
https://docs.microsoft.com/en-us/cpp/build/prolog-and-epilog?view=msvc-170
As a result of this problem, any crash within the x64 assembly code of libdav1d will not have any call stack information, as the stack unwinder won't know what to do.
Yasm supports generating this metadata, but the code would need to be retrofitted to use these.
By the way, the same is true of Windows ARM64, but I don't think libdav1d supports assembly on that yet.