Log Message:
libdiscid: update to 0.6.4.

libdiscid-0.6.4:

- LIB-69: Revert "Use discid_feature enum in discid_read_sparse". Fixes
  compiler errors with C++.

libdiscid-0.6.3:

 - LIB-66: fix for Debian kFreeBSD
 - Haiku platform support (TOC only)
 - Use discid_feature enum in discid_read_sparse
 - Fixed building with CMake on macOS
 - LIB-68: provide macOS universal2 binaries with support for both
           x86_64 and arm64
 - LIB-67: Source tarball with updated autotools configuration
 - CMake: Use GNUInstallDirs to determine install location
 - CMake 2.8.12 is now the minimum required version