package/mpg123: security bump to version 1.25.12

>From the release notes:
- Fix an out-of-bounds read of maximal two bytes for truncated RVA2 frames
  (oss-fuzz-bug 15975). The earlier fix around the same location needed
  one thought more. Actually, another though was needed, oss-fuzz-bug 16009
  documents the incomplete fix.

- Fix an invalid write of one zero byte for empty ID3v2 frames that demand
  de-unsyncing (oss-fuzz-bug 16050).

- Fix dynamic build with gcc -fsanitize=address (check for all dl functions
  before deciding that separate -ldl is not needed).

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>