Refactor Byte4 unpacking.

Change-Id: I82f8215ce4366e0795ce249b4d8f6c8e391af96c
Reviewed-on: https://swiftshader-review.googlesource.com/8568
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/Reactor/Reactor.hpp

diff --git a/src/Reactor/Reactor.hpp b/src/Reactor/Reactor.hpp
index 74a3f6c..cfb005c 100644
--- a/src/Reactor/Reactor.hpp
+++ b/src/Reactor/Reactor.hpp
@@ -564,6 +564,7 @@
 	RValue<Byte8> AddSat(RValue<Byte8> x, RValue<Byte8> y);
 	RValue<Byte8> SubSat(RValue<Byte8> x, RValue<Byte8> y);
 	RValue<Short4> Unpack(RValue<Byte4> x);
+	RValue<Short4> Unpack(RValue<Byte4> x, RValue<Byte4> y);
 	RValue<Short4> UnpackLow(RValue<Byte8> x, RValue<Byte8> y);
 	RValue<Short4> UnpackHigh(RValue<Byte8> x, RValue<Byte8> y);
 	RValue<Int> SignMask(RValue<Byte8> x);