Format of LS_cache file:
------------------------

1 guint32: magic (==0x4C536430 == 'LSd0')
1 guint32: compressed size of the list in this file (in bytes) (=N)
1 guint32: size required to decompress the list in this file (in bytes)
1 guint32: compression algorithm
1 time_t:  local time when the share list was retrieved
1 guint64: size of the shared files.
N bytes: the compressed share list

Note: the magic value and all binary values are stored with the endianness of
the local CPU, no conversions are performed.

