Bug fix: Compilation failure with NO_VSYNC_OPENGL=1

Fix compilation failure with NO_VSYNC_OPENGL=1, caused by one
incorrectly placed "#endif" in "src/common.h".

common.h

@@ -127,8 +127,9 @@
 #include <dbus/dbus.h>
 #endif
 
-// libGL
 #ifdef CONFIG_VSYNC_OPENGL
+
+// libGL
 #if defined(CONFIG_VSYNC_OPENGL_GLSL) || defined(CONFIG_VSYNC_OPENGL_FBO)
 #define GL_GLEXT_PROTOTYPES
 #endif
@@ -145,6 +146,8 @@
 #define GLX_BACK_BUFFER_AGE_EXT 0x20F4
 #endif
 
+#endif
+
 // === Macros ===
 
 #define MSTR_(s)        #s
@@ -2485,8 +2488,6 @@ c2_matchd(session_t *ps, win *w, const c2_lptr_t *condlst,
 
 ///@}
 
-#endif
-
 /**
  * @brief Dump the given data to a file.
  */