Confirm that install directory is identical
before and after this simplifying patch.
```bash
hg clone <<Eigen>>
mkdir eigen-bld
cd eigen-bld
cmake ../Eigen -DCMAKE_INSTALL_PREFIX:PATH=/tmp/bef
make install
find /tmp/pre_eigen_modernize >/tmp/bef
# Apply this patch
cmake ../Eigen -DCMAKE_INSTALL_PREFIX:PATH=/tmp/aft
make install
find /tmp/post_eigen_modernize |sed 's/post_e/pre_e/g' >/tmp/aft
diff /tmp/bef /tmp/aft
```