[gnome-system-monitor] Add support for libsystemd

[Michael Biebl <mbiebl src gnome org>]

commit 31d37f521d3efdb338b6ec4f83f3dbef68958aa1
Author: Michael Biebl <biebl debian org>
Date:   Mon May 18 23:49:50 2015 +0200

    Add support for libsystemd
    
    In systemd v209 the various libsystemd-* libraries were merged into a
    single libsystemd library. So first check for this library and fall back
    to libsystemd-login if not found.
    While at it, simplify the check by bumping the minimum required version
    to v44.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=749560

 configure.ac |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 817e49b..db4e203 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,9 +37,7 @@ GIOMM_REQUIRED=2.27
 GLIBMM_REQUIRED=2.27
 LIBXML_REQUIRED=2.0
 RSVG_REQUIRED=2.35
-SYSTEMD_REQUIRED=38
-# systemd v43 used the C++ keyword 'class' as a function parameter. This breaks the build for C++ programs.
-SYSTEMD_EXCLUDED=43
+SYSTEMD_REQUIRED=44
 
 PKG_CHECK_MODULES(GSM,
   glib-2.0 >= $GLIB_REQUIRED
@@ -68,13 +66,13 @@ PKG_CHECK_MODULES(SCRIPTS, glib-2.0 >= $GLIB_REQUIRED)
 have_systemd=no
 AC_ARG_ENABLE(systemd, AS_HELP_STRING([--disable-systemd], [disable systemd support]),,enable_systemd=no)
 if test "x$enable_systemd" != "xno"; then
-        PKG_CHECK_MODULES(SYSTEMD, [ libsystemd-login >= $SYSTEMD_REQUIRED ],
-                                   [ PKG_CHECK_MODULES(SYSTEMD_EX, [ libsystemd-login = $SYSTEMD_EXCLUDED ],
-                                                                   AC_MSG_ERROR([*** systemd v43 found but 
it has a bug in its header files (uses C++ keyword)]), # Can't use systemd v43 
-                                                                   [AC_DEFINE(HAVE_SYSTEMD, 1, [Define if 
systemd is available]) have_systemd=yes])],
-                                   have_systemd=no)
+        PKG_CHECK_MODULES(SYSTEMD, [libsystemd], [have_systemd=yes],
+                                   [PKG_CHECK_MODULES(SYSTEMD, [libsystemd-login >= $SYSTEMD_REQUIRED],
+                                   [have_systemd=yes])])
         if test "x$have_systemd" = xno; then
                 AC_MSG_ERROR([*** systemd support requested but libraries not found])
+        else
+                AC_DEFINE(HAVE_SYSTEMD, 1, [Define if systemd is available])
         fi
 fi
 AM_CONDITIONAL(HAVE_SYSTEMD, [test "$have_systemd" = "yes"])