plugins: add missing callbacks to version history

The discontinuity and system call filter callbacks were not reflected in
the versioning comments before. The callbacks have been introduced in
aac73d85d2 and
5ed628d1d3, respectively.

Signed-off-by: Florian Hofhammer <florian.hofhammer@epfl.ch>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Link: https://lore.kernel.org/qemu-devel/c4ecefb4-8769-403f-8420-8bce42e43e13@epfl.ch
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

include/plugins/qemu-plugin.h

@@ -77,6 +77,9 @@ typedef uint64_t qemu_plugin_id_t;
  * version 6:
  * - changed return value of qemu_plugin_{read,write}_register from int to bool
  * - added qemu_plugin_set_pc
+ * - added disconinuity callback API (for interrupts, exceptions, host calls)
+ * - added syscall filter callback API, which allows skipping syscalls and
+ *   setting custom syscall return values
  */
 
 extern QEMU_PLUGIN_EXPORT int qemu_plugin_version;