loader: bug 12992: extension and layer support

Much of layers and loader updated to work with
final extension and layer mechanism.
Not everything is working here.
diff --git a/icd/intel/extension_info.h b/icd/intel/extension_info.h
index ff9fc80..e6538e2 100644
--- a/icd/intel/extension_info.h
+++ b/icd/intel/extension_info.h
@@ -53,5 +53,5 @@
 
 bool compare_vk_extension_properties(
         const VkExtensionProperties *op1,
-        const VkExtensionProperties *op2);
+        const char                  *extName);
 #endif /* EXTENSION_INFO_H */