Add basic Vulkan support

Added GLFW_INCLUDE_VULKAN.  Added glfwVulkanSupported,
glfwGetRequiredInstanceExtensions, glfwGetInstanceProcAddress,
glfwGetPhysicalDevicePresentationSupport and glfwCreateWindowSurface.
Added port of LunarG SDK tri example.

src/wl_platform.h

@@ -29,6 +29,21 @@
 
 #include <wayland-client.h>
 #include <xkbcommon/xkbcommon.h>
+#include <dlfcn.h>
+
+typedef VkFlags VkWaylandSurfaceCreateFlagsKHR;
+
+typedef struct VkWaylandSurfaceCreateInfoKHR
+{
+    VkStructureType                 sType;
+    const void*                     pNext;
+    VkWaylandSurfaceCreateFlagsKHR  flags;
+    struct wl_display*              display;
+    struct wl_surface*              surface;
+} VkWaylandSurfaceCreateInfoKHR;
+
+typedef VkResult (APIENTRY *PFN_vkCreateWaylandSurfaceKHR)(VkInstance,const VkWaylandSurfaceCreateInfoKHR*,const VkAllocationCallbacks*,VkSurfaceKHR*);
+typedef VkBool32 (APIENTRY *PFN_vkGetPhysicalDeviceWaylandPresentationSupportKHR)(VkPhysicalDevice,uint32_t,struct wl_display*);
 
 #include "posix_tls.h"
 #include "posix_time.h"
@@ -41,6 +56,10 @@
  #error "The Wayland backend depends on EGL platform support"
 #endif
 
+#define _glfw_dlopen(name) dlopen(name, RTLD_LAZY | RTLD_LOCAL)
+#define _glfw_dlclose(handle) dlclose(handle)
+#define _glfw_dlsym(handle, name) dlsym(handle, name)
+
 #define _GLFW_EGL_NATIVE_WINDOW         ((EGLNativeWindowType) window->wl.native)
 #define _GLFW_EGL_NATIVE_DISPLAY        ((EGLNativeDisplayType) _glfw.wl.display)
 
@@ -75,6 +94,7 @@ typedef struct _GLFWwindowWayland
     _GLFWmonitor**              monitors;
     int                         monitorsCount;
     int                         monitorsSize;
+
 } _GLFWwindowWayland;