[glom] Use libxml++-3.0.

[Murray Cumming <murrayc src gnome org>]

commit cfdf9fcf3af8bc0d73316e6c8655e574143c7261
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Sep 18 10:46:02 2015 +0200

    Use libxml++-3.0.

 configure.ac              |    2 +-
 glom/libglom/xml_utils.cc |   12 +++++++++---
 glom/libglom/xml_utils.h  |    4 +++-
 3 files changed, 13 insertions(+), 5 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index ef30dca..bc717f8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -159,7 +159,7 @@ AS_IF([test "x$glom_enable_postgresql" = xyes],
 
 
 # Libraries used by libglom:
-REQUIRED_LIBGLOM_LIBS='giomm-2.4 >= 2.46.1 libxml++-2.6 >= 2.24.0 libxslt >= 1.1.10 pygobject-3.0 >= 2.29.0 
libgdamm-5.0 >= 4.99.10 libgda-5.0 >= 5.2.1 libgda-postgres-5.0 libgda-postgres-5.0 libgda-mysql-5.0 
libarchive >= 3.0'
+REQUIRED_LIBGLOM_LIBS='giomm-2.4 >= 2.46.1 libxml++-3.0 >= 2.24.0 libxslt >= 1.1.10 pygobject-3.0 >= 2.29.0 
libgdamm-5.0 >= 4.99.10 libgda-5.0 >= 5.2.1 libgda-postgres-5.0 libgda-postgres-5.0 libgda-mysql-5.0 
libarchive >= 3.0'
 
 AS_IF([test "x$glom_host_win32" != xyes],
       [REQUIRED_LIBGLOM_LIBS="$REQUIRED_LIBGLOM_LIBS libepc-1.0 >= 0.4.0"])
diff --git a/glom/libglom/xml_utils.cc b/glom/libglom/xml_utils.cc
index 6ea99e0..85d0950 100644
--- a/glom/libglom/xml_utils.cc
+++ b/glom/libglom/xml_utils.cc
@@ -61,9 +61,15 @@ void set_node_attribute_value(xmlpp::Element* node, const Glib::ustring& strAttr
   }
 }
 
-xmlpp::Element* get_node_child_named(const xmlpp::Element* node, const Glib::ustring& strName)
+xmlpp::Element* get_node_child_named(xmlpp::Element* node, const Glib::ustring& strName)
 {
-  xmlpp::Element* nodeResult = nullptr;
+  auto result = get_node_child_named(const_cast<const xmlpp::Element*>(node), strName);
+  return const_cast<xmlpp::Element*>(result);
+}
+
+const xmlpp::Element* get_node_child_named(const xmlpp::Element* node, const Glib::ustring& strName)
+{
+  const xmlpp::Element* nodeResult = nullptr;
 
   if(node)
   { 
@@ -74,7 +80,7 @@ xmlpp::Element* get_node_child_named(const xmlpp::Element* node, const Glib::ust
     //as well as Elements with the name "text".
     for(const auto& item : list)
     {
-      nodeResult = dynamic_cast<xmlpp::Element*>(item);  
+      nodeResult = dynamic_cast<const xmlpp::Element*>(item);
       if(nodeResult)
         return nodeResult;
     }                       
diff --git a/glom/libglom/xml_utils.h b/glom/libglom/xml_utils.h
index d09210c..e96ac83 100644
--- a/glom/libglom/xml_utils.h
+++ b/glom/libglom/xml_utils.h
@@ -34,7 +34,9 @@ namespace XmlUtils
 Glib::ustring get_node_attribute_value(const xmlpp::Element* node, const Glib::ustring& strAttributeName);
 void set_node_attribute_value(xmlpp::Element* node, const Glib::ustring& strAttributeName, const 
Glib::ustring& strValue);
 
-xmlpp::Element* get_node_child_named(const xmlpp::Element* node, const Glib::ustring& strName);
+xmlpp::Element* get_node_child_named(xmlpp::Element* node, const Glib::ustring& strName);
+const xmlpp::Element* get_node_child_named(const xmlpp::Element* node, const Glib::ustring& strName);
+
 xmlpp::Element* get_node_child_named_with_add(xmlpp::Element* node, const Glib::ustring& strName);
 
 /// If the attribute is not there, then the default will be returned.