Mpv: lower minimum required version
Currently the minimum required version of libmpv in CMakeLists.txt is set to 2.3.0, that is the current version. In reality the libmpv API calls we are using are stable since version 1.9.0. Lower the required version accordingly.
Context:
- libmpv annotated client API changes
- the source itself, containing "since" tags
- List of symbols we are currently using:
mpv_create
mpv_set_option_string
mpv_initialize
mpv_set_wakeup_callback
mpv_terminate_destroy
mpv_command_async
mpv_error_string
mpv_wait_event
MPV_EVENT_NONE
MPV_EVENT_END_FILE
mpv_event_end_file->error // Since API version 1.9.