Use safe-struct chain info copy (#158)

This fixes use of multiple layers, which were failing to create an 
instance if more than one layer was in use.

When we refactored the code to use safe-struct to avoid const-casting 
in layer code we patched the incorrect chain info, modifying the 
original user chain info rather than modifying the the safe-struct clone. 

This happens to work for a single layer because the driver doesn't use
the chain, but it fails as soon as you have multiple layers because the 
chain is never advanced and getProcAddr points at the wrong layer.

Author: solidpixel

source_common/framework/manual_functions.cpp

@@ -784,6 +784,10 @@ VKAPI_ATTR VkResult VKAPI_CALL layer_vkCreateInstance<default_tag>(const VkInsta
         LAYER_LOG("Requested instance extension list: [%u] = %s", i, newCreateInfo->ppEnabledExtensionNames[i]);
     }
 
+    // Get the new chain info so we modify our safe copy, not the original
+    chainInfo = getChainInfo(newCreateInfo);
+
+    // Advance the link info for the next element on the chain
     chainInfo->u.pLayerInfo = chainInfo->u.pLayerInfo->pNext;
     auto result = fpCreateInstance(newCreateInfo, pAllocator, pInstance);
     if (result != VK_SUCCESS)
@@ -874,6 +878,9 @@ VKAPI_ATTR VkResult VKAPI_CALL layer_vkCreateDevice<default_tag>(VkPhysicalDevic
         return VK_ERROR_INITIALIZATION_FAILED;
     }
 
+    // Get the new chain info so we modify our safe copy, not the original
+    chainInfo = getChainInfo(newCreateInfo);
+
     // Advance the link info for the next element on the chain
     chainInfo->u.pLayerInfo = chainInfo->u.pLayerInfo->pNext;
     auto res = fpCreateDevice(physicalDevice, newCreateInfo, pAllocator, pDevice);