WGL: Fix pixel format count in a Parallels VM

In a Parallels VM wglGetPixelFormatAttribivARB returns fewer pixel
formats than DescribePixelFormat.  This broke context creation on
Windows in Parallels since the changes in
2c0f34b60f7c7a07183ed71754b0156ece3b6c1b.  The previous version of the
code worked accidentally.

This adds a workaround by iterating through the minimum of both counts.
It should have no effect when running on conforming implementations.

Tested on Parallels by @ dougbinks.

Closes #2191
Fixes #2406
Fixes #2467

CONTRIBUTORS.md

@@ -47,6 +47,7 @@ video tutorials.
  - Bailey Cosier
  - Noel Cower
  - CuriouserThing
+ - Bill Currie
  - Jason Daly
  - danhambleton
  - Jarrod Davis
@@ -166,6 +167,7 @@ video tutorials.
  - Pascal Muetschard
  - James Murphy
  - Julian Møller
+ - NateIsStalling
  - ndogxj
  - F. Nedelec
  - n3rdopolis

src/wgl_context.c

@@ -115,6 +115,23 @@ static int choosePixelFormatWGL(_GLFWwindow* window,
             if (_glfw.wgl.EXT_colorspace)
                 ADD_ATTRIB(WGL_COLORSPACE_EXT);
         }
+
+        // NOTE: In a Parallels VM WGL_ARB_pixel_format returns fewer pixel formats than
+        //       DescribePixelFormat, violating the guarantees of the extension spec
+        // HACK: Iterate through the minimum of both counts
+
+        const int attrib = WGL_NUMBER_PIXEL_FORMATS_ARB;
+        int extensionCount;
+
+        if (!wglGetPixelFormatAttribivARB(window->context.wgl.dc,
+                                          1, 0, 1, &attrib, &extensionCount))
+        {
+            _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
+                                 "WGL: Failed to retrieve pixel format attribute");
+            return 0;
+        }
+
+        nativeCount = _glfw_min(nativeCount, extensionCount);
     }
 
     usableConfigs = _glfw_calloc(nativeCount, sizeof(_GLFWfbconfig));