Created attachment 4700
Build fix on GNU/Hurd
The compilation of xfce4-power-manager 1.2.0 fails on GNU/Hurd, because of the following two includes not available:
They have been added with rev 8a30a7b  (bug #8712), and according to the bug they were moved from a linux-only block to a non-specific one because they were needed for FreeBSD. Given that it seems they are not needed on Linux (sysctl() is not used on Linux blocks in that file), and removing them causes no build failure on Linux, my suggestion is to include them only on FreeBSD, just below <sys/stat.h>.
Attached there is a patch (compilation tested only on Linux and Hurd, not on FreeBSD though) for it.
Pushed a commit that should fix this issue for you: http://git.xfce.org/xfce/xfce4-power-manager/commit/?id=af69bc562f1f7dbc8f94e246779beb7a8bb45904
Let us know if this fixes it for you and feel free to report if have any more issues with GNU/Hurd (or any kernel + userland :)