Fix broken GLEW initialization. Initialize GLEW twice, once to get GLX

extensions, once to get final context extensions.

Not so nice because we get a warning on startup from GLEW, but at least
it GL extensions should work now.

intern/ghost/intern/GHOST_ContextGLX.cpp

@@ -102,6 +102,7 @@ GHOST_ContextGLX::~GHOST_ContextGLX()
 		}
 
 #ifdef WITH_GLEW_MX
+		if (m_glxewContext)
 			delete m_glxewContext;
 #endif
 	}
@@ -135,6 +136,7 @@ void GHOST_ContextGLX::initContextGLXEW()
 	glxewContext = new GLXEWContext;
 	memset(glxewContext, 0, sizeof(GLXEWContext));
 
+	if (m_glxewContext)
 		delete m_glxewContext;
 	m_glxewContext = glxewContext;
 #endif
@@ -262,6 +264,9 @@ GHOST_TSuccess GHOST_ContextGLX::initializeDrawingContext()
 		initClearGL();
 		::glXSwapBuffers(m_display, m_window);
 
+		/* re initialize to get the extensions properly */
+		initContextGLXEW();
+
 		success = GHOST_kSuccess;
 	}
 	else {