Added documentation for VK_KHR_dedicated_allocation extension.

src/vk_mem_alloc.h

@@ -45,6 +45,7 @@ Table of contents:
   - \subpage defragmentation
   - \subpage lost_allocations
 - \subpage configuration
+  - \subpage VK_KHR_dedicated_allocation
 - \subpage thread_safety
 
 See also:
@@ -390,6 +391,70 @@ To do it, fill optional member VmaAllocatorCreateInfo::pHeapSizeLimit.
 
 
 
+\page VK_KHR_dedicated_allocation VK_KHR_dedicated_allocation
+
+VK_KHR_dedicated_allocation is a Vulkan extension which can be used to improve
+performance on some GPUs. It augments Vulkan API with possibility to query
+driver whether it prefers particular buffer or image to have its own, dedicated
+allocation (separate `VkDeviceMemory` block) for better efficiency - to be able
+to do some internal optimizations.
+
+The extension is supported by this library. It will be used automatically when
+enabled. To enable it:
+
+1 . When creating Vulkan device, check if following 2 device extensions are
+supported (call `vkEnumerateDeviceExtensionProperties()`).
+If yes, enable them (fill `VkDeviceCreateInfo::ppEnabledExtensionNames`).
+
+- VK_KHR_get_memory_requirements2
+- VK_KHR_dedicated_allocation
+
+If you enabled these extensions:
+
+2 . Query device for pointers to following 2 extension functions, using
+`vkGetDeviceProcAddr()`. Pass them in structure VmaVulkanFunctions while creating
+your `VmaAllocator`.
+
+- `vkGetBufferMemoryRequirements2KHR`
+- `vkGetImageMemoryRequirements2KHR`
+
+Other members of this structure can be null as long as you leave
+`VMA_STATIC_VULKAN_FUNCTIONS` defined to 1, which is the default.
+
+\code
+VmaVulkanFunctions vulkanFunctions = {};
+vulkanFunctions.vkGetBufferMemoryRequirements2KHR =
+    (PFN_vkGetBufferMemoryRequirements2KHR)vkGetDeviceProcAddr(device, "vkGetBufferMemoryRequirements2KHR");
+vulkanFunctions.vkGetImageMemoryRequirements2KHR =
+    (PFN_vkGetImageMemoryRequirements2KHR)vkGetDeviceProcAddr(device, "vkGetImageMemoryRequirements2KHR");
+    
+VmaAllocatorCreateInfo allocatorInfo = {};
+allocatorInfo.pVulkanFunctions = &vulkanFunctions;
+// Fill other members of allocatorInfo...
+\endcode
+
+
+3 . Use `VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT` flag when creating
+your `VmaAllocator` to inform the library that you enabled required extensions
+and you want the library to use them.
+
+\code
+allocatorInfo.flags |= VMA_ALLOCATOR_CREATE_KHR_DEDICATED_ALLOCATION_BIT;
+
+vmaCreateAllocator(&allocatorInfo, &allocator);
+\endcode
+
+
+That's all. The extension will be automatically used whenever you create a
+buffer using vmaCreateBuffer() or image using vmaCreateImage().
+
+To learn more about this extension, see:
+
+- [VK_KHR_dedicated_allocation in Vulkan specification](https://www.khronos.org/registry/vulkan/specs/1.0-extensions/html/vkspec.html#VK_KHR_dedicated_allocation)
+- [VK_KHR_dedicated_allocation unofficial manual](http://asawicki.info/articles/VK_KHR_dedicated_allocation.php5)
+
+
+
 \page thread_safety Thread safety
 
 - The library has no global state, so separate `VmaAllocator` objects can be used