WGL: Fix count of displayable pixel formats

We only care about displayable pixel formats (as defined in
WGL_ARB_pixel_format) for window context creation.

This changes pixel format enumeration to ignore non-displayable formats,
which are specified to be listed after displayable ones, by always using
the return value of DescribePixelFormat as the pixel format count.

src/wgl_context.c

@@ -72,18 +72,13 @@ static int choosePixelFormatWGL(_GLFWwindow* window,
     int attribs[40];
     int values[sizeof(attribs) / sizeof(attribs[0])];
 
+    nativeCount = DescribePixelFormat(window->context.wgl.dc,
+                                      1,
+                                      sizeof(PIXELFORMATDESCRIPTOR),
+                                      NULL);
+
     if (_glfw.wgl.ARB_pixel_format)
     {
-        const int attrib = WGL_NUMBER_PIXEL_FORMATS_ARB;
-
-        if (!wglGetPixelFormatAttribivARB(window->context.wgl.dc,
-                                          1, 0, 1, &attrib, &nativeCount))
-        {
-            _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
-                                 "WGL: Failed to retrieve pixel format attribute");
-            return 0;
-        }
-
         ADD_ATTRIB(WGL_SUPPORT_OPENGL_ARB);
         ADD_ATTRIB(WGL_DRAW_TO_WINDOW_ARB);
         ADD_ATTRIB(WGL_PIXEL_TYPE_ARB);
@@ -121,13 +116,6 @@ static int choosePixelFormatWGL(_GLFWwindow* window,
                 ADD_ATTRIB(WGL_COLORSPACE_EXT);
         }
     }
-    else
-    {
-        nativeCount = DescribePixelFormat(window->context.wgl.dc,
-                                          1,
-                                          sizeof(PIXELFORMATDESCRIPTOR),
-                                          NULL);
-    }
 
     usableConfigs = _glfw_calloc(nativeCount, sizeof(_GLFWfbconfig));