install properly the free-list headers

include/dmmlib/CMakeLists.txt

@@ -17,12 +17,14 @@ if(WITH_KNOBS)
 endif(WITH_KNOBS)
 
 if(RAW_BLOCKS_TYPE STREQUAL "freelist")
-  set(dmmlib_HDRS
-    ${dmmlib_HDRS}
-    freelist/initialize.h
-    freelist/freelist.h
-    freelist/freelist_rb.h
-    )
+  install(
+    DIRECTORY
+      freelist
+    DESTINATION
+      ${INCLUDE_INSTALL_DIR}/${APPLICATION_NAME}
+    COMPONENT
+      headers
+  )
 endif(RAW_BLOCKS_TYPE STREQUAL "freelist")
 
 install(