Feature-freeze exception for taglib and taglib-extras

TagLib 1.6 was just released with a very significant number of fixes, including critical fixes that prevent tags or audio data from being corrupted in user files. A partial changelog is here -- keep in mind that this changelog was only started when a new maintainer stepped up to finish the 1.6 release, and does not contain the many other fixes since 1.5:

TagLib 1.6
==========

1.6:

 * New CMake option to build a static version - ENABLE_STATIC.
 * Added support for disabling dllimport/dllexport on Windows using the
   TAGLIB_STATIC macro.
 * Support for parsing the obsolete 'gnre' MP4 atom.
 * New cpp macros TAGLIB_WITH_MP4 and TAGLIB_WITH_ASF to determin if
   TagLib was built with MP4/ASF support.

1.6 RC1:

 * Split Ogg packets larger than 64k into multiple pages. (BUG:171957)
 * TagLib can now use FLAC padding block. (BUG:107659)
 * ID3v2.2 frames are now not incorrectly saved. (BUG:176373)
 * Support for ID3v2.2 PIC frames. (BUG:167786)
 * Fixed a bug in ByteVectorList::split().
 * XiphComment::year() now falls back to YEAR if DATE doesn't exist
   and XiphComment::year() falls back to TRACKNUM if TRACKNUMBER doesn't
   exist. (BUG:144396)
 * Improved ID3v2.3 genre parsing. (BUG:188578)
 * Better checking of corrupted ID3v2 APIC data. (BUG:168382)
 * Bitrate calculating using the Xing header now uses floating point
   numbers. (BUG:172556)
 * New TagLib::String method rfind().
 * Added support for MP4 file format with iTunes-style metadata [optional].
 * Added support for ASF (WMA) file format [optional].
 * Fixed crash when saving a Locator APEv2 tag. (BUG:169810)
 * Fixed a possible crash in the non-const version of String::operator[]
   and in String::operator+=. (BUG:169389)
 * Added support for PRIV ID3v2 frames.
 * Empty ID3v2 genres are no longer treated as numeric ID3v1 genres.
 * Added support for the POPM (rating/playcount) ID3v2 frame.
 * Generic RIFF file format support:
   * Support for AIFF files with ID3v2 tags.
   * Support for WAV files with ID3v2 tags.
 * Fixed crash on handling unsupported ID3v2 frames, e.g. on encrypted
   frames. (BUG:161721)
 * Fixed overflow while calculating bitrate of FLAC files with a very
   high bitrate.

In addition to the significant number of bug fixes, this version includes support for MP4 and ASF files. This is the same exact code that has lived in taglib-extras prior to the TagLib 1.6 release, so it is not untested code. Although it is disabled by default, this is purely because some distributions asked for this in the past (many have changed their minds; Fedora Legal for instance decided that the formats posed no patent problems); since Ubuntu has included taglib-extras already, there is no reason not to build this code.

Including TagLib 1.6 will also require including an update to taglib-extras-1.0, removing the redundant code to avoid namespace conflicts. The change in taglib-extras is API/ABI incompatible; however, the only package using it is Amarok (which has been granted an exception and which I will fix). JuK has an Ubuntu-specific patch using taglib-extras, however I can either fix the patch or it can simply be dropped.

It is *highly* recommended that these changes make it into Karmic; otherwise, not only does it keep users' data at risk from severe TagLib bugs, but it will become much harder to package any future packages (including Amarok) that want to use the new taglib formats and taglib-extras API/ABI.