configure: Add WUtil flags to avoid compilation error

configure: Add WUtil flags to avoid compilation error

Just running ./configure; make lead to this compilation error
on openSUSE 12.1:

make[3]: Entering directory `/home/mafra/Window_Maker/fsviewer-app-0.2.6/src'
gcc  -g -O2 -I -I/usr/local/include  -L/usr/lib64 -L/usr/lib64 -o FSViewer FSViewer.o files.o FSFileBrowser.o list.o misc.o prop.o timestampWidget.o attribsInspector.o editInspector
xeInspector.o extnInspector.o iconInspector.o viewInspector.o FSBrowser.o FSPanel.o FSUtils.o FSMenu.o FSFileView.o FSInspector.o magic.o DnD.o FSPathView.o xmodifier.o FSFinder.o F
eButton.o FSMCList.o FSPrefs.o -Lregexp -lregx -lnsl -lWINGs -lWMaker -lXft -lXmu  -lwraster -ltiff -lXpm -lpng -ljpeg -lXext -lX11 -lm
/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/bin/ld: FSViewer.o: undefined reference to symbol 'WMGetStandardUserDefaults'
/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/bin/ld: note: 'WMGetStandardUserDefaults' is defined in DSO /usr/lib64/libWUtil.so.2 so try adding it to the linke
mmand line
/usr/lib64/libWUtil.so.2: could not read symbols: Invalid operation
collect2: ld returned 1 exit status
make[3]: *** [FSViewer] Fehler 1
make[3]: Leaving directory `/home/mafra/Window_Maker/fsviewer-app-0.2.6/src'
make[2]: *** [all-recursive] Fehler 1
make[2]: Leaving directory `/home/mafra/Window_Maker/fsviewer-app-0.2.6/src'
make[1]: *** [all] Fehler 2

One way to fix this is to use the following option to configure

--with-extralibs=-lWUtil

but it's much better if the configuration script already does that
for you.

So I automated that by using 'get-wutil-flags', and now just running
./configure is fine.

Signed-off-by: Carlos R. Mafra <crmafra@gmail.com>