Always check for Boost::System, and do that before the Boost::Filesystem check

ac/ax_boost_filesystem_dependencies.m4

@@ -1,32 +0,0 @@
-AC_DEFUN([AX_BOOST_FILESYSTEM_DEPENDENCIES],[
-  AC_CACHE_CHECK([if Boost::Filesystem requires Boost::System],
-                 [ax_cv_boost_dependencies_system],[
-    CPPFLAGS_SAVED="$CPPFLAGS"
-    CPPFLAGS="$CPPFLAGS $BOOST_CPPFLAGS"
-    export CPPFLAGS
-
-    LDFLAGS_SAVED="$LDFLAGS"
-    LDFLAGS="$LDFLAGS $BOOST_LDFLAGS"
-    export LDFLAGS
-
-    LIBS_SAVED="$LIBS"
-    LIBS="$LIBS $BOOST_FILESYSTEM_LIB"
-    export LIBS
-
-    AC_LANG_PUSH(C++)
-    AC_LINK_IFELSE([
-      AC_LANG_PROGRAM([
-          #include <boost/filesystem.hpp>
-        ],[
-          boost::filesystem::path p1("/etc/hosts");
-          int i = boost::filesystem::basename(p1).length();
-        ])],
-      [ax_cv_boost_dependencies_system=no],
-      [ax_cv_boost_dependencies_system=yes])
-    AC_LANG_POP()
-
-    CPPFLAGS="$CPPFLAGS_SAVED"
-    LDFLAGS="$LDFLAGS_SAVED"
-    LIBS="$LIBS_SAVED"
-  ])
-])

ac/boost.m4

@@ -1,6 +1,11 @@
 # boost's headers must be present.
 AX_BOOST_BASE([1.34.0])
 
+# boost::system can be absend for older versions. However, the test
+# for boost::filesystem might fail if boost::system is not available
+# with newer versions.
+AX_BOOST_SYSTEM()
+
 # boost::filesystem must be present.
 AX_BOOST_FILESYSTEM()
 
@@ -8,17 +13,6 @@ if test x"$ax_cv_boost_filesystem" != "xyes"; then
   AC_MSG_ERROR(The Boost Filesystem library was not found.)
 fi
 
-# boost::system must be present if boost::filesystem needs it.
-AX_BOOST_FILESYSTEM_DEPENDENCIES()
-
-if test x"$ax_cv_boost_dependencies_system" = "xyes"; then
-  AX_BOOST_SYSTEM()
-
-  if test x"$ax_cv_boost_system" != "xyes"; then
-    AC_MSG_ERROR(The Boost System library was not found.)
-  fi
-fi
-
 # boost::regex must be present.
 AX_BOOST_REGEX()
 

configure.in

@@ -38,7 +38,6 @@ m4_include(ac/qt4.m4)
 m4_include(ac/magic.m4)
 m4_include(ac/ax_boost_base.m4)
 m4_include(ac/ax_boost_filesystem.m4)
-m4_include(ac/ax_boost_filesystem_dependencies.m4)
 m4_include(ac/ax_boost_foreach.m4)
 m4_include(ac/ax_boost_regex.m4)
 m4_include(ac/ax_boost_system.m4)