Generalize 4x32-bit vector swizzling.

Generalize 4x32-bit vector swizzling.

This enables swizzling of Int4 and UInt4 types using swizzle operators.

Change-Id: I83fe5b472433d84a7b092e18eb78a919fb39b03b
Reviewed-on: https://swiftshader-review.googlesource.com/8530
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>