Convert a string into a tag_type enum.

The tag_id3.c library supports both the documented "TSO2" tag, and the
inofficial TXXX/ALBUMARTISTSORT.

The Vorbis/FLAC decoder automatically supports the new tag, without
further change.

When a song was in the database twice (which shouldn't happen), and
the first song had no tag items, MPD calledd tag_free(NULL).  Add a
check to that source location, and an assertion to tag_free().

strcasecmp() is locale dependent, making it a bad choice for internal
string comparisons.

Use GLib the logging functions g_debug(), g_error() instead.

This updates the copyright header to all be the same, which is
pretty much an update of where to mail request for a copy of the GPL
and the years of the MPD project. This also puts all committers under
'The Music Player Project' umbrella. These entries should go
individually in the AUTHORS file, for consistancy.

Renamed functions and variables.

Overwrite invalid UTF-8 sequences with question marks.

There's no point in declaring num_items as a uint8_t, it doesn't save
any space, due to padding.  This allows us to lift the articial "255
items" limitation.

Renamed numOfItems to num_items.

This variable doesn't have a role since 80799fa8.

On some platforms, g_free() must be used for memory allocated by
GLib.  This patch intends to correct a lot of occurrences, but is
probably not complete.

All config_get_block_*() functions should accept constant config_param
pointers.

config_get_string() is easier to use than config_get_param() because
it unpacks the config_param struct.

Added all important id tags from the MusicBrainz wiki:

 http://musicbrainz.org/doc/MusicBrainzTag

This should automatically enable its suport in the vorbis and flac
decoder plugins.

Renamed functions, types, variables.

Added TAG_ITEM_ALBUM_ARTIST.

With this patch, MPD should be able to read the (inofficial)
"ALBUMARTIST" Vorbis comment.  Implementations in other decoder
plugins will follow soon.

Use g_strndup() instead of g_memdup().

Pass NULL instead of &error to g_convert().  We're not interested in
the error object.

tag_merges() merges the data from two tag objects into one.

Don't use g_strescape(), because it escapes all non-ASCII characters.
Add a new function which clears all non-printable characters, not just
"newline".

This always allocates strings on the heap, but we can delete the
stripReturnChar() function now.

tag_has_type() checks whether the tag contains one or more items with
the specified type.

Don't use the deprecated functions from utils.h.

Eliminate code already provided by GLib.

Return NULL instead of the input value if there is nothing to fix.
This way, the caller doesn't have to use the xfree() hack.

Removed duplicated code.

When there are standardized headers, use these instead of the bloated
os_compat.h.

avoid some redundant clearing logic as well, since the tag is
getting freed.

Seeing the "mpd_" prefix _everywhere_ is mind-numbing as the
mind needs to retrain itself to skip over the first 4 tokens of
a type to get to its meaning.  So avoid having extra characters
on my terminal to make it easier to follow code at 2:30 am in
the morning.

Please report any new issues you may come across on Free
toolchains.  I realize how difficult it can be to build/maintain
cross-compiling toolchains and I have no intention of forcing
people to upgrade their toolchains to build mpd.

Tested with gcc 2.95.4 and and gcc 4.3.1 on x86-32.

With a large music database, the linear string collection in
tagTracker.c becomes very slow.  We implemented that in a
quick'n'dirty fashion when we removed tree.c, and now we rewrite it
using the fast hashed string set.

Gah, it seems like doing sizeof here either way is error
prone.  Too easy to leave out a '*' character we can
forget.