When parsing the songlength database fails, the code forgot to free
the memory allocated by the raw file data.

The caller is responsible fro freeing GError objects.  That
g_error_free() call was missing in two places.

The error handler dereferences GError*, but did not retrieve that
object from g_file_get_contents().

[mk: added autoconf test; fixed songlen_data_size type]

It makes no difference right now, but we're about to add an endianness
flag and will want to make sure it's correctly initialised every 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.

[mk: fixed whitespace errors; use delete_song() instead of
songvec_delete()]