[evince] libdocument: Fix constness

[Christian Persch <chpe src gnome org>]

commit de3ff975a4319cfe9dee673edd5537109eea45c6
Author: Christian Persch <chpe gnome org>
Date:   Sat Jun 8 23:59:50 2013 +0200

    libdocument: Fix constness
    
    ev-file-helpers.c:89:25: warning: assignment discards 'const' qualifier from pointer target type [enabled 
by default]

 libdocument/ev-file-helpers.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/libdocument/ev-file-helpers.c b/libdocument/ev-file-helpers.c
index ad75b95..902ed40 100644
--- a/libdocument/ev-file-helpers.c
+++ b/libdocument/ev-file-helpers.c
@@ -84,7 +84,8 @@ _ev_tmp_dir (GError **error)
 {
 
         if (tmp_dir == NULL) {
-                gchar *dirname, *prgname;
+                gchar *dirname;
+                const gchar *prgname;
 
                 prgname = g_get_prgname ();
                 dirname = g_strdup_printf ("%s-%u", prgname ? prgname : "unknown", getpid ());