adding entry point to soft driver, adding C test

src/vulkan/Instance.zig

@@ -1,13 +1,24 @@
 const std = @import("std");
 const vk = @import("vulkan");
-const PhysicalDevice = @import("PhysicalDevice").PhysicalDevice;
+const PhysicalDevice = @import("PhysicalDevice.zig").PhysicalDevice;
 const Object = @import("object.zig").Object;
 
 pub const Instance = extern struct {
     const Self = @This();
-    const ObjectType: vk.ObjectType = .instance;
+    pub const ObjectType: vk.ObjectType = .instance;
+    pub const vtable: *const VTable = .{};
 
     object: Object,
-    physical_devices: std.ArrayList(*PhysicalDevice),
+    //physical_devices: std.ArrayList(*PhysicalDevice),
     alloc_callbacks: vk.AllocationCallbacks,
+
+    pub const VTable = struct {
+        createInstance: ?vk.PfnCreateInstance,
+        destroyInstance: ?vk.PfnDestroyInstance,
+        enumeratePhysicalDevices: ?vk.PfnEnumeratePhysicalDevices,
+        getInstanceProcAddr: ?vk.PfnGetInstanceProcAddr,
+        enumerateInstanceVersion: ?vk.PfnEnumerateInstanceVersion,
+        //enumerateInstanceLayerProperties: vk.PfnEnumerateInstanceProperties,
+        enumerateInstanceExtensionProperties: ?vk.PfnEnumerateInstanceExtensionProperties,
+    };
 };