configure: rename OpenGL feature to GLX

As the probe now actually checks for the availability of GLX, rename it
accordingly. The only user of this feature is the milkymist-tmu2 model.

Signed-off-by: Michael Walle <michael@walle.cc>
diff --git a/configure b/configure
index d44d6b8..3505040 100755
--- a/configure
+++ b/configure
@@ -217,7 +217,7 @@
 rbd=""
 smartcard_nss=""
 usb_redir=""
-opengl=""
+glx=""
 zlib="yes"
 guest_agent="yes"
 want_tools="yes"
@@ -858,9 +858,9 @@
   ;;
   --enable-vhost-net) vhost_net="yes"
   ;;
-  --disable-opengl) opengl="no"
+  --disable-glx) glx="no"
   ;;
-  --enable-opengl) opengl="yes"
+  --enable-glx) glx="yes"
   ;;
   --disable-rbd) rbd="no"
   ;;
@@ -2435,9 +2435,9 @@
 fi
 
 ##########################################
-# opengl probe, used by milkymist-tmu2
-if test "$opengl" != "no" ; then
-  opengl_libs="-lGL -lX11"
+# GLX probe, used by milkymist-tmu2
+if test "$glx" != "no" ; then
+  glx_libs="-lGL -lX11"
   cat > $TMPC << EOF
 #include <X11/Xlib.h>
 #include <GL/gl.h>
@@ -2445,13 +2445,13 @@
 int main(void) { glBegin(0); glXQueryVersion(0,0,0); return 0; }
 EOF
   if compile_prog "" "-lGL -lX11" ; then
-    opengl=yes
+    glx=yes
   else
-    if test "$opengl" = "yes" ; then
-      feature_not_found "opengl"
+    if test "$glx" = "yes" ; then
+      feature_not_found "glx"
     fi
-    opengl_libs=
-    opengl=no
+    glx_libs=
+    glx=no
   fi
 fi
 
@@ -3429,7 +3429,7 @@
 echo "xfsctl support    $xfs"
 echo "nss used          $smartcard_nss"
 echo "usb net redir     $usb_redir"
-echo "OpenGL support    $opengl"
+echo "GLX support       $glx"
 echo "libiscsi support  $libiscsi"
 echo "build guest agent $guest_agent"
 echo "seccomp support   $seccomp"
@@ -3740,8 +3740,8 @@
   echo "CONFIG_USB_REDIR=y" >> $config_host_mak
 fi
 
-if test "$opengl" = "yes" ; then
-  echo "CONFIG_OPENGL=y" >> $config_host_mak
+if test "$glx" = "yes" ; then
+  echo "CONFIG_GLX=y" >> $config_host_mak
 fi
 
 if test "$libiscsi" = "yes" ; then
@@ -4019,7 +4019,7 @@
     target_nptl="yes"
   ;;
   lm32)
-    target_libs_softmmu="$opengl_libs"
+    target_libs_softmmu="$glx_libs"
   ;;
   m68k)
     bflt="yes"