Drop glib requrirement to 2.28

This lets it build on more currently-released systems like Fedora 15.

src/libotutil/ot-gio-utils.c

@@ -21,7 +21,6 @@
 
 #include "config.h"
 
-#include <glib-unix.h>
 #include <gio/gio.h>
 #include <gio/gunixinputstream.h>
 

src/libotutil/ot-unix-utils.c

@@ -23,7 +23,6 @@
 
 #include "ot-unix-utils.h"
 
-#include <glib-unix.h>
 #include <gio/gio.h>
 #include <gio/gunixoutputstream.h>
 
@@ -205,7 +204,7 @@ ot_util_set_error_from_errno (GError **error,
                               gint     saved_errno)
 {
   g_set_error_literal (error,
-                       G_UNIX_ERROR,
+                       G_IO_ERROR,
                        0,
                        g_strerror (saved_errno));
   errno = saved_errno;

src/libotutil/ot-unix-utils.h

@@ -23,10 +23,10 @@
 #define __OSTREE_UNIX_UTILS_H__
 
 #include <gio/gio.h>
-#include <glib-unix.h>
 
 /* I just put all this shit here. Sue me. */
 #include <sys/types.h>
+#include <errno.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <dirent.h>