[lightsoff] build fix

[Thomas Hindoe Paaboel Andersen <thomashpa src gnome org>]

commit 2824bbfaa65e6efb9cdd054c9ce4543ecccaea47
Author: Thomas Hindoe Paaboel Andersen <phomes gmail com>
Date:   Wed Oct 10 13:36:54 2012 +0200

    build fix

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 9eb0e12..47972d7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,8 @@ PKG_CHECK_MODULES(LIGHTSOFF, [
   clutter-gtk-1.0 >= $CLUTTER_REQUIRED
 ])
 
+AC_CHECK_LIB([m],[floor])
+
 dnl ###########################################################################
 dnl Internationalization
 dnl ###########################################################################