fix install of IterativeSolvers module

unsupported/Eigen/src/CMakeLists.txt

diff --git a/unsupported/Eigen/src/CMakeLists.txt b/unsupported/Eigen/src/CMakeLists.txt
index c9f8144..67ef0a9 100644
--- a/unsupported/Eigen/src/CMakeLists.txt
+++ b/unsupported/Eigen/src/CMakeLists.txt
@@ -1 +1 @@
-# ADD_SUBDIRECTORY(Foo)
+ADD_SUBDIRECTORY(IterativeSolvers)

unsupported/Eigen/src/IterativeSolvers/CMakeLists.txt

diff --git a/unsupported/Eigen/src/IterativeSolvers/CMakeLists.txt b/unsupported/Eigen/src/IterativeSolvers/CMakeLists.txt
new file mode 100644
index 0000000..024b02f
--- /dev/null
+++ b/unsupported/Eigen/src/IterativeSolvers/CMakeLists.txt
@@ -0,0 +1,6 @@
+FILE(GLOB Eigen_IterativeSolvers_SRCS "*.h")
+
+INSTALL(FILES
+  ${Eigen_IterativeSolvers_SRCS}
+  DESTINATION ${INCLUDE_INSTALL_DIR}/unsupported/Eigen/src/IterativeSolvers
+  )