io: convert QIOChannelBuffer to use uint8_t instead of char

The QIOChannelBuffer struct uses a 'char *' for its data
buffer. It will give simpler type compatibility with the
migration APIs if it uses 'uint8_t *' instead, avoiding
several casts.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
diff --git a/io/channel-buffer.c b/io/channel-buffer.c
index 0f7c567..3e5117b 100644
--- a/io/channel-buffer.c
+++ b/io/channel-buffer.c
@@ -32,7 +32,7 @@
     ioc = QIO_CHANNEL_BUFFER(object_new(TYPE_QIO_CHANNEL_BUFFER));
 
     if (capacity) {
-        ioc->data = g_new0(char, capacity);
+        ioc->data = g_new0(uint8_t, capacity);
         ioc->capacity = capacity;
     }