The source package fails to build from source on the hurd-* and kfreebsd-*
arches with the following error.

/bin/bash ../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H -I. -I..  -I../include/ -I../src -Wall -Werror
-DBUILDING_FRAME -D_FORTIFY_SOURCE=2 -std=c++0x -fvisibility=hidden  -fvisibility=hidden -I/usr/include/pixman-1
-I/usr/include/xorg   -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -c -o
handle.lo handle.cpp
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I.. -I../include/ -I../src -Wall -Werror -DBUILDING_FRAME
-D_FORTIFY_SOURCE=2 -std=c++0x -fvisibility=hidden -fvisibility=hidden -I/usr/include/pixman-1 -I/usr/include/xorg -g
-O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -c handle.cpp  -fPIC -DPIC -o
.libs/handle.o
handle.cpp:25:25: fatal error: sys/eventfd.h: No such file or directory
compilation terminated.
make[3]: *** [handle.lo] Error 1

[Stephen M. Webb 2013-06-05]

As far as I can tell, it is because the code uses the linux specific
call to eventfd().  I guess the code need a port to select() or Hurd and
FreeBSD need to gain support for eventfd to fix this issue.