[PATCH 4/7] d3dcompiler: Unwrap swizzles from the left-hand side of an assignment.

[Matteo Bruni]

Signed-off-by: Matteo Bruni <mbruni at codeweavers.com>
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I stared at invert_swizzle() an inordinate amount of time and I
eventually convinced myself it's correct, or at least sensible. I'm
going to require more swizzle tests when the compiler will actually
start to work. I assume you already have a bunch for this but,
obviously, tests with multiple LHS swizzles would be particularly
interesting.