tdf#100455 check for minimal dconf version

Change-Id: I8e164bb4afc221cefd93d519569cdefa4486349f
diff --git a/configure.ac b/configure.ac
index 97794c8..590e326 100644
--- a/configure.ac
+++ b/configure.ac
@@ -10587,7 +10587,7 @@ AC_SUBST([COLLADA2GLTF_LIBS])
AC_SUBST([SYSTEM_COLLADA2GLTF])

if test "$enable_dconf" != no; then
    PKG_CHECK_MODULES([DCONF], [dconf], [], [
    PKG_CHECK_MODULES([DCONF], [dconf >= 0.15.2], [], [
        if test "$enable_dconf" = yes; then
            AC_MSG_ERROR([dconf not found])
        else