libcacard: Fix compilation for older versions of glib (bug #1258168)

See https://bugs.launchpad.net/bugs/1258168

libcacard/vscclient.c: In function 'do_socket_read':
libcacard/vscclient.c:410: warning: implicit declaration of function 'g_warn_if_reached'
libcacard/vscclient.c:410: warning: nested extern declaration of 'g_warn_if_reached'
libcacard/vscclient.c: In function 'main':
libcacard/vscclient.c:763: warning: implicit declaration of function 'g_byte_array_unref'
libcacard/vscclient.c:763: warning: nested extern declaration of 'g_byte_array_unref'
...
libcacard/vscclient.o: In function `do_socket_read':
libcacard/vscclient.c:410: undefined reference to `g_warn_if_reached'
libcacard/vscclient.o: In function `main':
libcacard/vscclient.c:763: undefined reference to `g_byte_array_unref'

g_warn_if_reached was added in glib 2.16, and g_byte_array_unref is
supported since glib 2.22. QEMU requires glib 2.12, so both names must
not be used.

Instead of showing a warning for code which should not be reached,
vscclient better stop running, so g_warn_if_reached is not useful for
vscclient.

In libcacard/vsclient.c, g_byte_array_unref can be replaced by
g_byte_array_free. This is not generally true, so adding a compatibility
layer in include/glib-compat.h is no option here.

Reported-by: Laurent Desnogues <[email protected]>
Reported-by: Don Slutz <[email protected]>
Signed-off-by: Stefan Weil <[email protected]>

libcacard/vscclient.c

@@ -407,7 +407,7 @@ do_socket_read(GIOChannel *source,
             }
             break;
         default:
-            g_warn_if_reached();
+            g_assert_not_reached();
             return FALSE;
         }
 
@@ -760,7 +760,7 @@ main(
 
     g_io_channel_unref(channel_stdin);
     g_io_channel_unref(channel_socket);
-    g_byte_array_unref(socket_to_send);
+    g_byte_array_free(socket_to_send, TRUE);
 
     closesocket(sock);
     return 0;