package/wavpack: security bump to version 5.4.0

package/wavpack: security bump to version 5.4.0

WavPack 5.4.0 contains a fix for CVE-2020-35738 wherein a specially
crafted WAV file could cause the WAVPACK command-line program to crash
with an out-of-bounds write (see issue #91).

Update hash of COPYING (update in year:
https://github.com/dbry/WavPack/commit/2ce3c069be548e82ea9c05741ace6583e549c6de)

https://github.com/dbry/WavPack/blob/5.4.0/NEWS

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>