The monitor handle could have become invalid just before the call to
GetDpiForMonitor. It was possible for both window and monitor content
scale queries.
This ensures both that an appropriate error is emitted and that the
retrieved values are zero on error.
Fixes#1615
This removes the GLFW_VULKAN_STATIC CMake option and the
_GLFW_VULKAN_STATIC configuration macro and replaces them with the
glfwInitVulkanLoader function, allowing a single library binary to
provide both behaviors.
This is based on the design from PR #1374 by @pmuetschard.
Closes#1374Closes#1890
