layers: Update PV codegen for Windows warning
layers: Update PV codegen for Windows warning

Code gen declarations of allowed_structs in nested scopes could cause
warnings in Windows.  Modified codegen to append the type name to
allowed_structs (eg allowed_structs_VkGraphicsPipelineCreateInfo) to
avoid name collisions.

Change-Id: I40bd57ff34dcd1df01d3606c79dacbe06b00f464

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers