Add command line flag to show list of snapshots.

This patch introduces the flag '-snapshot-list', which causes the
emulator to output a table of snapshots in the currently mounted
snapshot storage file.

The snapshot file is accessed with a very simple driver for the Qcow2
file system, independent of Qemu's block driver framework. This way,
the flag is available in the emulator-ui builds as well. Using Qemu's
framework would have resulted in adding a lot of Qemu dependencies to
the UI build, which we are explicitly trying to avoid.

Change-Id: I059b9ac53e2f8e051757a5c637761eccf8ea17cb
diff --git a/android/snapshot.h b/android/snapshot.h
new file mode 100644
index 0000000..be03818
--- /dev/null
+++ b/android/snapshot.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SNAPSHOTS_H_
+#define SNAPSHOTS_H_
+
+#include "config/config.h"
+
+#if CONFIG_ANDROID_SNAPSHOTS
+
+/* Prints a table with information on the snapshot stored in the file
+ * 'snapstorage', then exit()s.
+ */
+void snapshot_print_and_exit( const char *snapstorage );
+
+#endif
+
+#endif /* SNAPSHOTS_H_ */