[gxml] Fix Meson header installation

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 29b23c73a48c6c9e5da35ca3c4c74df59d14aef8
Author: Yannick Inizan <inizan yannick gmail com>
Date:   Fri Sep 1 15:14:23 2017 -0500

    Fix Meson header installation

 gxml/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gxml/meson.build b/gxml/meson.build
index ee74e5d..281c257 100644
--- a/gxml/meson.build
+++ b/gxml/meson.build
@@ -143,7 +143,7 @@ lib = library(VERSIONED_PROJECT_NAME,
        install : true,
        install_dir : [
                get_option('libdir'),
-               join_paths (get_option('includedir'), 'gxml','gxml-@0@'.format (API_VERSION)),
+               join_paths (get_option('includedir'), 'gxml-@0@'.format (API_VERSION), 'gxml'),
                vapidir,
                true
        ])