Duplicate struct members when generating on darwin

[johanhenriksson]

Trying to run the generation on macos now, having a few issues. Im using vk.xml version 1.3.242

• struct.go line ~7950, duplicated code:

	var psl_pStages *_vkPipelineShaderStageCreateInfo
	if len(s.PStages) > 0 {
		sl_pStages := make([]_vkPipelineShaderStageCreateInfo, len(s.PStages))
		for i, v := range s.PStages {
			sl_pStages[i] = *(v.Vulkanize())
		}
		psl_pStages = &sl_pStages[0]
	}

related struct member pStages is also duplicated.

• struct.go line ~20877, PipelineCacheCreateInfo has duplicate member InitialDataSize.

• struct.go line ~22138, PipelineShaderStageCreateInfo has duplicate member PName

[bbredesen]

Possible root cause is the new vulkansc API in 1.3.242, which duplicates some types and struct members with slightly different definitions. (If correct, then this becomes a general issue, and not related to generating on mac.)