After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

Convert a string into a tag_type enum.

Clear the colon.  This simplifies all attribute parsers, because they
can now use strcmp() instead of strncmp().

Fix a minor memory leak.

Changed songvec_load() to song_load().  Added start and end markers
for each song.  Removed the "key" line, it's redundant.

Use a single GString buffer object in all functions loading the
database.  Enlarge it automatically for long lines.  This eliminates
the maximum line length for tag values.  There is still an upper limit
of 512 kB to prevent denial of service, but that's reasonable I guess.

The line buffer had a fixed size of 5 kB, and was allocated on the
stack.  This was too small for some users.  As a hotfix, we're
increasing the buffer size to 32 kB now, allocated on the heap.  In
MPD 0.16, we'll switch to dynamic allocation.

Renamed functions.

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().

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 numOfItems to num_items.

If a tag value is an empty string, the space after the colon was
removed by g_strchomp().  Fix this by removing the space check and
using g_strchug() on the return value.

The matchesAnMpdTagItemKey() API becomes more powerful and flexible if
the return value is the value pointer instead of a boolean.  It also
removes (invalid and dangerous) assumptions about the string from its
caller.

matchesAnMpdTagItemKey() broke when two tag items had the same prefix,
because it did not check if the tag name ended after the prefix.  Add
a check for the colon and the space after the tag name.

Replaced myFgets() with fgets() + g_strchomp().

CamelCase is ugly, rename the functions.

CamelCase is ugly...  rename all functions.

Provide separate constructors for creating a remote song, a local
song, and one for loading data from a song file.  This way, we can add
more assertions.

Again, a data type which can be forward-declared.

The struct can be forward-declared by other headers, which relaxes the
header dependencies.

songvec_for_each() has locking, use it instead of manually iterating
over the songvec items.

We already know if a song is a URL or not based on whether it
has parentDir defined or not.  Hopefully one day in the future
we can drop HTTP support from MPD entirely when an HTTP
filesystem comes along and we can access streams via open(2).

Reduce the number of allocations we make, so there's less
pressure on the allocator and less overhead to keep track
of the allocations in.

It didn't save us any lines of code nor did it do anything
useful since we would overwrite everything anyways.

Any pruned files will be noticed during update and pruned
from the live database, so this inefficient function can
go away and never come back.

Pruning is very expensive and we won't need it in the future
anyways.  This brings startup back to previous speeds (before
songvec changes).

Our linked-list implementation is wasteful and the
SongList isn't modified enough to benefit from being a linked
list.  So use a more compact array of song pointers which
saves ~200K on a library with ~9K songs (on x86-32).

Currently, when the tag cache is being serialized to hard disk, the
stdio buffer is flushed before every song, because tag_print.c
performs unbuffered writes on the raw file descriptor.  Unfortunately,
the fdprintf() API allows buffered I/O only for a client connection by
looking up the client pointer owning the file descriptor - for stdio,
this is not possible.  To re-enable proper stdio buffering, we have to
duplicate the tag_print.c code without fprintf() instead of our custom
fdprintf() hack.  Add this duplicated code to tag_save.c.

Move everything which dumps song information (via tag_print.c) to a
separate source file.  song_print.c gets code which writes song data
to the client; song_save.c is responsible for serializing songs from
the tag cache.

Move everything which dumps a tag to a file descriptor to tag_print.c.
This relaxes dependencies and splits the code into smaller parts.

clearMpdTag could be called on a tag that was still in a
tag_begin_add transaction before tag_end_add is called.  This
was causing free() to attempt to operate on bulk.items; which is
un-free()-able.  Now instead we unmark the bulk.busy to avoid
committing the tags to the heap only to be immediately freed.

Additionally, we need to remember to call tag_end_add() when
a song is updated before we NULL song->tag to avoid tripping
an assertion the next time tag_begin_add() is called.

If many tag_items are added at once while the tag cache is being
loaded, manage these items in a static fixed list, instead of
reallocating the list with every newly created item.  This reduces
heap fragmentation.

Massif results again:

 mk before:  total 12,837,632; useful 10,626,383; extra 2,211,249
 mk now:     total 12,736,720; useful 10,626,383; extra 2,110,337

The "useful" value is the same since this patch only changes the way
we allocate the same amount of memory, but heap fragmentation was
reduced by 5%.

The function newNullSong() is only used internally in song.c.