And specify whether generic tags are being scanned.

This code has been moved to LoadFromArchive().

Load APE/ID3 tags from archives.

This commit adds support for APE/ID3 tags from NFS/SMB files.

See http://bugs.musicpd.org/view.php?id=4270

Avoid duplicate AllocatedPath::FromUTF8() invocations in two callers.

Don't pass Path::c_str() to tag_stream_scan() which requires a UTF-8
string.

Reduce some unnecessary overhead.

Replaces StatFile(), with a portable data object.

This commit finally allows the database update to scan remote files,
e.g. using the smbclient storage plugin.  However, it is not yet
possible to configure that, therefore the feature is not accessible
yet.

Prepare for UPnP songs that retain there database identity.

The Song class is only used for database songs now.  A Song without a
Directory is not possible anymore.

Reduces overhead because we need to manage only one memory allocation.
According to valgrind/massif, we save 7%.