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 )
diff --git a/aos/build/externals.gyp b/aos/build/externals.gyp
index 863df98..264bdbb 100644
--- a/aos/build/externals.gyp
+++ b/aos/build/externals.gyp
@@ -14,7 +14,7 @@
     }]],
 
 # These versions have to be kept in sync with the ones in download_externals.sh.
-    'eigen_version': '3.1.3',
+    'eigen_version': '3.2.1',
     'gtest_version': '1.6.0-p1',
     'onejar_version': '0.97',
     'ctemplate_version': '129',
diff --git a/output/downloaded/.gitignore b/output/downloaded/.gitignore
index d91a4c2..69ab810 100644
--- a/output/downloaded/.gitignore
+++ b/output/downloaded/.gitignore
@@ -1,7 +1,7 @@
 /ctemplate-129.tar.gz
 /ctemplate-129/
-/eigen-3.1.3.tar.bz2
-/eigen-3.1.3/
+/eigen-3.2.1.tar.bz2
+/eigen-3.2.1/
 /gccdist.zip
 /gccdist/
 /gtest-1.6.0-p1/