[libgepub] tests: Fixed signedness warnings

[Daniel Garcia Moreno <danigm src gnome org>]

commit a260fabda4e72697839f6f9f5251fedf340493c1
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Jun 22 10:13:33 2017 +0200

    tests: Fixed signedness warnings
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784081

 tests/test-gepub.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/tests/test-gepub.c b/tests/test-gepub.c
index c04e403..fd257bb 100644
--- a/tests/test-gepub.c
+++ b/tests/test-gepub.c
@@ -151,7 +151,7 @@ test_open (const char *path)
 static void
 find_xhtml (gchar *key, GepubResource *value, gpointer data)
 {
-    guchar **d = (guchar **)data;
+    gchar **d = (gchar **)data;
     if (g_strcmp0 (value->mime, "application/xhtml+xml") == 0) {
         *d = value->uri;
     }
@@ -163,7 +163,7 @@ test_read (const char *path)
     GepubArchive *a;
     GList *list_files = NULL;
     const guchar *buffer;
-    guchar *file = NULL;
+    gchar *file = NULL;
     gsize bufsize;
     GBytes *bytes;
     GepubDoc *doc;