[gtkglext] Fail at configure time if OpenGL is missing.

[Braden McDaniel <bradenmcd src gnome org>]

commit 98ffc0d8a3ac5eb5e62f30cdb90305e132d5fd4f
Author: Braden McDaniel <braden endoframe com>
Date:   Fri Oct 15 01:08:24 2010 -0400

    Fail at configure time if OpenGL is missing.

 configure.ac |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6c198e1..69500e7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -235,6 +235,9 @@ PKG_CHECK_MODULES([PANGOFT2], [pangoft2], ,
 GLIB_MKENUMS="`$PKG_CONFIG --variable=glib_mkenums glib-2.0`"
 AC_SUBST(GLIB_MKENUMS)
 
+AX_CHECK_GL
+AS_IF([test X$no_gl = Xyes],
+      [AC_MSG_FAILURE([OpenGL is required.])])
 AX_CHECK_GLU
 # FIXME: AX_CHECK_GLU's behavior diverges from common autoconf conventions
 AM_CONDITIONAL([GLU],[test "$no_glu" != yes])