opus: Update to version 1.5.1

opus: Update to version 1.5.1

- Update from version 1.4 to 1.5.1
- Update of rootfile
- Changelog
    1.5.1
	 Opus 1.5.1 fixes the meson build that was broken in 1.5.
    1.5
        Opus 1.5 is the first release to make extended use of ML in the encoder and
         decoder. You can read all the details in the release demo page. In summary, major
         changes since 1.4 include:
            Significant improvement to packet loss robustness using Deep Redundancy (DRED)
            Improved packet loss concealment through Deep PLC
            Low-bitrate speech quality enhancement down to 6 kb/s wideband
            Improved x86 (AVX2) and Arm (Neon) optimizations
            Support for 4th and 5th order ambisonics
        In addition to the improvements above, this release includes many minor bug fixes.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>