Eigen3 compiler warnings

When building libbarrett, the following warning comes up many times:

/usr/include/eigen3/Eigen/src/Core/DenseBase.h:103:10: warning: enumeral mismatch in conditional expression: ‘Eigen::internal::size_at_compile_time<3, 1>::<anonymous enum>’ vs ‘Eigen::internal::traits<Eigen::Matrix<double, 3, 1> >::<anonymous enum>’ [-Wenum-compare]

These can be suppressed by adding -Wno-enum-compare to line 51 of cmake/modules/FindXenomai.cmake.

Not sure if this is a libbarrett error or related to the version of Eigen. The libeigen3-dev package installs Eigen 3.0.5, and there are some newer releases of Eigen3 now.