Improve earlyinit check for PyOpenGL

Importing OpenGL alone doesn't actually load libgl, it only checks that the
package is here. If libgl is missing, we'd later get an exception.

(cherry picked from commit b81474d2fd)

qutebrowser/misc/earlyinit.py

@@ -342,7 +342,7 @@ def check_libraries(backend):
         modules['PyQt5.QtWebEngineWidgets'] = _missing_str("QtWebEngine",
                                                            webengine=True)
         modules['PyQt5.QtOpenGL'] = _missing_str("PyQt5.QtOpenGL")
-        modules['OpenGL'] = _missing_str("PyOpenGL")
+        modules['OpenGL.GL'] = _missing_str("PyOpenGL")
     else:
         assert backend == 'webkit'
         modules['PyQt5.QtWebKit'] = _missing_str("PyQt5.QtWebKit")