Declare two named elements.  An enum should not be used as an array
index, as this is error prone.

By declaring the variable-length array to have a nominal size of 1,
struct TagPoolSlot shrinks from 24 bytes to 16 bytes, because "ref"
and "item" now both fit in one machine word.

The "packed" attribute triggers a clang 4.0 warning, and it's not
necessary.  All we want is correct allocation of this
dynamically-sized struct.

The "packed" attribute triggers a clang 4.0 warning, and it's not
necessary.  All we want is correct allocation of this
dynamically-sized struct.

When a reference counter is at its limit, don't allocate a new
TagPoolSlot - that would result in many TagPoolSlot instances with
ref==1.  This in turn would make the linked list very very large,
which means quadratic runtime for many operations.

Fixes deadlock.

Prepare for APE tag support on userspace NFS/SMB/CIFS mounts.

Prepare for ID3 support on userspace NFS/SMB/CIFS mounts.

Use a 128 byte buffer instead of reading 10 bytes first and then 118.