[gtk+] configure: test have_docbook_style != yes, not have_docbook_dtd

[Alexander Larsson <alexl src gnome org>]

commit 94a149c8ea69ecfacd4d605afd7ad9c1d9f439dd
Author: Alexander Larsson <alexl redhat com>
Date:   Wed Jun 17 17:35:18 2015 +0200

    configure: test have_docbook_style != yes, not have_docbook_dtd

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index df2b223..b99af91 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1738,7 +1738,7 @@ if test "$enable_man" != no; then
   dnl check for DocBook XSL stylesheets in the local catalog
   JH_CHECK_XML_CATALOG([http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl],
      [DocBook XSL Stylesheets], [have_docbook_style=yes],[have_docbook_style=no])
-  if test "$have_docbook_dtd" != yes; then
+  if test "$have_docbook_style" != yes; then
     if test "$enable_man" = yes ; then
       AC_MSG_ERROR([DocBook XSL Stylesheets are required for --enable-man])
     fi