All close() implementations must call this method.

Major API redesign: don't let the caller allocate the input_stream
object.  Let each input plugin allocate its own (derived/extended)
input_stream pointer.  The "data" attribute can now be removed, and
all input plugins simply cast the input_stream pointer to their own
structure (with an "struct input_stream base" as the first attribute).

Make the input_stream implementation hold a reference on the
archive_file object.  Allow the caller to "close" the archive_file
object immediately, no matter if the open_stream() method has
succeeded or not.

The archive plugin should decide this.

Reduce the number of malloc()/free() calls.

Don't use the bz2_archive_file object for the input_stream.

Don't use the iso9660_archive_file object for the input_stream.

Don't use the zzip_archive object for the input_stream.

Make archive_file a "real" struct, extended by all plugins.  Add the
plugin pointer to it.  Wrap all method calls in functions.

Moved the archive plugin "extern" declarations into each plugin
header.

Use the raw struct name instead.

Based on libiso9660.

Use g_path_get_basename() instead of manually filtering the path
name.  Big advantage: g_path_get_basename() cannot fail.

Don't attempt to fill the whole buffer in the read() method, return
whatever libbz2 provides with the first successful BZ2_bzDecompress().

Use the raw struct name.

This plugin is based on libzzip.

Free the "context" pointer in the method archive_plugin.close().

Fixes a memory leak: the "archive" input plugin opens the archive, but
never closes it.  This patch moves the responsibility for doing that
to archive_plugin.open_stream().  This is an slight internal API
change, but it is the simplest and least intrusive fix for the memory
leak.

g_free(NULL) is allowed.

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.

The "off_t" type may change when you enable or disable large file
support on 32 bit platforms.  This caused severe ABI problems within
MPD when we enabled LFS for the first time: two sources included
config.h and sys/types.h in different order, and had different off_t
sizes - leading to memory corruption because of ABI incompatibility.
This patch attempts to get rid of all public "off_t" uses: it removes
"off_t" from the input_stream ABI/API, and switches to GLib's 64 bit
"goffset" type.  This may hurt 32 bit embedded platforms a tiny bit,
but that's not even measurable.

The second parameter of zzip_dir_open() is a pointer.  Pass the NULL
pointer instead of 0 (with implicit conversion at compile time).

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.

Start to separate private from public input_stream API.

Make those two methods optional to implement, and let input_stream.c
provide fallbacks.  The buffer() method will be removed one day, and
there is now only one implementation left (input_curl.c).

The open_stream() method opens the input_stream.  This allows the
archive plugin to do its own initialization, and it also allows it to
use input_stream.data.  We can remove input_stream.archive now, which
was unnatural to have in the first place.