'test -e' is not supported on Solaris, replace with '-f' or '-d'.

diff --git a/configure.in b/configure.in
index b8ee0f4..761b96f 100644
--- a/configure.in
+++ b/configure.in
@@ -265,7 +265,7 @@
     dnl Check for the presence of OpenGL
     if test $OPENGL = "yes" -o $OPENGL = "normal"
     then
-        if test -e /usr/X11R6/lib/libGL.a -a ! -e /usr/X11R6/lib/libGL.so
+        if test -f /usr/X11R6/lib/libGL.a -a ! -f /usr/X11R6/lib/libGL.so
         then
 	    AC_MSG_ERROR([/usr/X11R6/lib/libGL.a is present on your system.
 This prevents linking to OpenGL. Delete the file and restart configure.])