[libgepub] lib: Fix signedness warnings in GepubArchive

[Daniel Garcia Moreno <danigm src gnome org>]

commit 5fd5bb27b6139996f063bfd7c56bfedb51c5bfc9
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Jun 22 10:11:21 2017 +0200

    lib: Fix signedness warnings in GepubArchive
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784081

 libgepub/gepub-archive.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgepub/gepub-archive.c b/libgepub/gepub-archive.c
index ba5bb15..21d8b9d 100644
--- a/libgepub/gepub-archive.c
+++ b/libgepub/gepub-archive.c
@@ -161,7 +161,7 @@ gepub_archive_get_root_file (GepubArchive *archive)
     xmlNode *root_element = NULL;
     xmlNode *root_node = NULL;
     GBytes *bytes;
-    const guchar *buffer;
+    const gchar *buffer;
     gsize bufsize;
     gchar *root_file = NULL;