add new key for dri section: exdriver

etc/MiniGUI.cfg

@@ -22,10 +22,13 @@
 
 [system]
 # GAL engine and default options
+# The equivalent environment variable: MG_GAL_ENGINE
 gal_engine=pc_xvfb
+# The equivalent environment variable: MG_DEFAULTMODE
 defaultmode=800x600-16bpp
 
 # IAL engine
+# The equivalent environment variable: MG_IAL_ENGINE
 ial_engine=pc_xvfb
 mdev=/dev/input/mice
 mtype=IMPS2
@@ -44,10 +47,15 @@ pixelformat=XR24
 
 # The DRI device
 device=/dev/dri/card0
+
 # The resolution of the display
 # It is defined in dots (physical pixels) per inch
 # The default value is 96.
 dpi=96
+
+# The filename of the shared library for the external driver.
+# The equivalent environment variable: MG_GAL_DRI_DRIVER
+exdriver=libdrm_minigui.so.1
 #}}
 
 #{{ifdef _MGIAL_LIBINPUT