#1 Fix underlink

[Tupone Alfredo]

See: https://bugs.gentoo.org/show_bug.cgi?id=367601 and http://blog.flameeyes.eu/2010/11/26/it-s-not-all-gold-that-shines-why-underlinking-is-a-bad-thing

This patch should fix the problem:

--- configure.ac.old 2011-05-24 08:45:49.197656941 +0200
+++ configure.ac 2011-05-24 08:46:13.685193761 +0200
@@ -101,6 +101,7 @@
AC_CHECK_LIB(GLU, gluNewQuadric, [ LDFLAGS="$LDFLAGS -lGLU" ],
[AC_MSG_ERROR([OpenGL libraries not found])
])
+LDFLAGS="$LDFLAGS -lm"

AC_CONFIG_FILES([Makefile])
AC_OUTPUT