[libxml++] Disable deprecated API in dependencies if --enable-warnings=fatal

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 09ca556d780fb3dad8cf9d8a1b37d3228fecaba0
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Wed Mar 4 10:53:23 2015 +0100

    Disable deprecated API in dependencies if --enable-warnings=fatal
    
    * configure.ac: Disable deprecated API in glib, glibmm and libsigc++ when
    building with --enable-warnings=fatal.
    * libxml++/validators/parser.cc: Put #include <glibmm/threads.h> first.
    Necessary when G_DISABLE_DEPRECATED is defined.

 configure.ac               |    3 ++-
 libxml++/parsers/parser.cc |    5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index fe880bf..6f69f81 100644
--- a/configure.ac
+++ b/configure.ac
@@ -42,7 +42,8 @@ MM_ARG_WITH_TAGFILE_DOC([glibmm-2.4.tag], [glibmm-2.4])
 # Evaluate the --enable-warnings=level option.
 MM_ARG_ENABLE_WARNINGS([LIBXMLXX_WXXFLAGS],
         [-Wall],
-        [-pedantic -Wall -Wextra -Wno-long-long])
+        [-pedantic -Wall -Wextra -Wno-long-long],
+        [G GLIBMM SIGCXX])
 
 # Offer the ability to omit some API from the library.
 MM_ARG_DISABLE_DEPRECATED_API([LIBXMLXX])
diff --git a/libxml++/parsers/parser.cc b/libxml++/parsers/parser.cc
index e32567e..f6f4fce 100644
--- a/libxml++/parsers/parser.cc
+++ b/libxml++/parsers/parser.cc
@@ -4,13 +4,16 @@
  * included with libxml++ as the file COPYING.
  */
 
+// Include glibmm/threads.h first. It must be the first file to include glib.h,
+// because it temporarily undefines G_DISABLE_DEPRECATED while it includes glib.h.
+#include <glibmm/threads.h> // For Glib::Threads::Mutex. Needed until the next API/ABI break.
+
 #include "libxml++/parsers/parser.h"
 
 #include <libxml/parser.h>
 
 #include <memory> //For auto_ptr.
 #include <map>
-#include <glibmm/threads.h> // For Glib::Threads::Mutex. Needed until the next API/ABI break.
 
 //TODO: See several TODOs in parser.h for changes at the next API/ABI break.