Avoid to call the imlib2-config that may be installed on the host system
(even when --with-imlib2-prefix or --with-imlib2-exec-prefix is passed to
the configure script), which totally screws up the resulting linker flags.

Inspired by: http://git.fluxbox.org/fluxbox.git/commit/?id=b178bed60b5bd8b2c9ed0cbc67fd729ff3820589

Signed-off-by: Samuel Martin <s.martin49@gmail.com>

--- fluxbox-1.3.2.orig/configure.in	2012-10-21 16:11:59.445749396 +0200
+++ fluxbox-1.3.2/configure.in	2012-10-21 16:35:27.658390856 +0200
@@ -443,8 +443,6 @@ if test x$enable_imlib2 = "xyes"; then
       [
          IMLIB2=true
          AC_DEFINE(HAVE_IMLIB2, [], [Imlib2 support])
-         IMLIB2_LIBS=`imlib2-config --libs`
-         IMLIB2_CFLAGS=`imlib2-config --cflags`
          LIBS="$LIBS $IMLIB2_LIBS"
          CXXFLAGS="$CXXFLAGS $IMLIB2_CFLAGS"
        ], [ AC_MSG_RESULT(no)]