updated Eigen version to get fix for bug 554
See <http://eigen.tuxfamily.org/bz/show_bug.cgi?id=554> for details. It
made claw_lib_test segfault on the BBB.
diff --git a/aos/build/download_externals.sh b/aos/build/download_externals.sh
index 9af583b..adb224c 100755
--- a/aos/build/download_externals.sh
+++ b/aos/build/download_externals.sh
@@ -44,7 +44,7 @@
[ -d ${GCCDIST} ] || ( cd ${EXTERNALS} && unzip -q ${GCCDIST}.zip )
# get eigen
-EIGEN_VERSION=3.1.3
+EIGEN_VERSION=3.2.1
EIGEN_DIR=${EXTERNALS}/eigen-${EIGEN_VERSION}
[ -f ${EIGEN_DIR}.tar.bz2 ] || wget http://bitbucket.org/eigen/eigen/get/${EIGEN_VERSION}.tar.bz2 -O ${EIGEN_DIR}.tar.bz2
[ -d ${EIGEN_DIR} ] || ( mkdir ${EIGEN_DIR} && tar --strip-components=1 -C ${EIGEN_DIR} -xf ${EIGEN_DIR}.tar.bz2 )