Truncate overlong tag info and replace newlines by spaces.

Truncate overlong tag info and replace newlines by spaces.

The tag info which is computed by the audio format handlers and stored
in the audio file table is read into a fixed-size buffer by the audio
file selector in open_and_update_audio_file(), passed to the server
process and then sent to the client via the stat command. It is not
interpreted at all during this process. In particular, it is not
essential for correctly streaming the audio file.

Vorbis comments and id3v2 tags have no size limit and may contain
arbitrary data which may lead to the following twi problems:

	- As noted by Gerrit Renker, if the tag info is too long
	to fit into the fixed-size buffer, the current code skips
	the audio file and removes it from the list of currently
	admissible files. So para_server fails to stream such files.

	- If the tag info contains newlines, these are included
	verbatim in the status output which may confuse para_audiod.

This patch truncates the tag info string if it does not fit into the
4K buffer and replaces newlines by spaces. This is a bit ugly but
avoids both of the above problems. It's still possible to retrieve
the complete tag info via the "ls -lv" command.