Updated libopenmpt to 0.2.8043.

libopenmpt 0.2-beta23 (2017-04-23)

    [Change] The libmpg123 binary download script on Windows now downloads libmpg123 1.24.0.
    [Change] MSVC builds of libopenmpt will now only load known DMO plugins.
    [Bug] foo_openmpt: Interpolation filter and volume ramping settings were confused in previous versions. This version resets both to the defaults.

(wiz)