Replace glad and the Vulkan SDK with glad2

This removes all dependencies from the GLFW test programs on the Vulkan
SDK.

It also removes support for linking the GLFW shared library (dynamic
library, DLL) against the Vulkan loader static library.

README.md

@@ -97,17 +97,12 @@ located in the `deps/` directory.
    with command-line options
  - [TinyCThread](https://github.com/tinycthread/tinycthread) for threaded
    examples
- - An OpenGL 3.2 core loader generated by
-   [glad](https://github.com/Dav1dde/glad) for examples using modern OpenGL
+ - [glad2](https://github.com/Dav1dde/glad) for loading OpenGL and Vulkan
+   functions
  - [linmath.h](https://github.com/datenwolf/linmath.h) for linear algebra in
    examples
  - [Nuklear](https://github.com/vurtun/nuklear) for test and example UI
  - [stb\_image\_write](https://github.com/nothings/stb) for writing images to disk
- - [Vulkan headers](https://www.khronos.org/registry/vulkan/) for Vulkan tests
-
-The Vulkan example additionally requires the LunarG Vulkan SDK to be installed,
-or it will not be included in the build.  On macOS you need to provide the path
-to the SDK manually as it has no standard installation location.
 
 The documentation is generated with [Doxygen](http://doxygen.org/) if CMake can
 find that tool.
@@ -196,6 +191,7 @@ information on what to include when reporting a bug.
 - Removed `GLFW_USE_MENUBAR` compile-time option
 - Removed requirement of at least one window for `glfwWaitEvents` and
   `glfwPostEmptyEvent` (#1317)
+- Removed all dependencies on the Vulkan SDK
 - Bugfix: Calling `glfwMaximizeWindow` on a full screen window was not ignored
 - Bugfix: `GLFW_INCLUDE_VULKAN` could not be combined with the corresponding
           OpenGL and OpenGL ES header macros
@@ -210,14 +206,11 @@ information on what to include when reporting a bug.
 - [Win32] Removed XInput circular deadzone from joystick axis data (#1045)
 - [Win32] Bugfix: Undecorated windows could not be iconified by the user (#861)
 - [Win32] Bugfix: Deadzone logic could underflow with some controllers (#910)
-- [Win32] Bugfix: Bitness test in `FindVulkan.cmake` was VS specific (#928)
 - [Win32] Bugfix: `glfwVulkanSupported` emitted an error on systems with
                   a loader but no ICD (#916)
 - [Win32] Bugfix: Non-iconified full sreeen windows did not prevent screen
                   blanking or password enabled screensavers (#851)
 - [Win32] Bugfix: Mouse capture logic lost secondary release messages (#954)
-- [Win32] Bugfix: The 32-bit Vulkan loader library static was not searched for
-- [Win32] Bugfix: Vulkan libraries have a new path as of SDK 1.0.42.0 (#956)
 - [Win32] Bugfix: Monitors with no display devices were not enumerated (#960)
 - [Win32] Bugfix: Monitor events were not emitted (#784)
 - [Win32] Bugfix: The DLL was installed to the wrong directory on Cygwin (#1035)