Check if the URI scheme is supported by MPD, and print an error
message if not.  Optimize the checks in "add" and "playlistadd".

Don't work with argv[1], give it the better name "uri".

Due to a typo, adding local files was always denied.

Disable the second playlist_append_file() invocation on WIN32.

There are no unix sockets on WIN32, and therefore no authentication.
WIN32 might have similar capabilities, but until we implement them,
disable that MPD feature.

Only include headers which are really needed.  os_compat.h aimed to
make MPD easily portable, but was never actually made portable.

gmtime_r() is not available.

When a client-specified URI has a scheme which is not supported, do
not try to open it as a local file, but provide a meaningful error
message.

printRemoteUrlHandlers() cannot fail, and does not need a return
value.

We want to remove gcc.h eventually. This takes care of all the G_GNUC_PRINTF
macros.

We shouldn't pass strerror() where a format string is expected.

The client may provide the names of idle events as arguments to the
"idle" command to inform MPD that it is only interested in these
events.

We don't need to sanitize the path, because the mapper already checks
for malformed paths.

Replace a custom data structure with a GLib one.

check_bool() accepts only "0" or "1".  The range check is superfluous.

Due to a logic error, no value was valid for the boolean value
parser.  Replace "||" with "&&".

The function deletePlaylist() shouldn't be in playlist.c.

The "long" result of strtol() was implicitly casted down to a 32 bit
integer.  Add some range checking instead.

Many command arguments must not be negative; add a separate
parser/checker function for that.  For the same reason, add
check_bool().  This eliminates two strange special cases handlers from
check_int().

There are some integers which have a "magic" -1 value which means
"undefined" or "nothing".  All others can be converted to unsigned,
since they must not contain a negative number.

Instead of returning 0 for success and -1 for failure, return true or
false.  This seems more natural.

Also add names for "error" and "ok".  I don't like passing anonymous
integer codes around.

This is not yet complete: lots of functions (e.g. in playlist.c)
follow the same convention of -1/0, and these have to be adapted, too.

http://xkcd.com/292/

Eliminate CamelCase in all public and static functions.

The typedef CommandHandlerFunction is only used once.  Move its type
into the command struct.

Send last modification timestamps to the client.  This allows the
client to see when another client modifies a stored playlist.

"listplaylists" returns a list of all stored playlists.  This command
seems more elaborate than listing them below "lsinfo".

The function print_spl_list() replaces the old function lsPlaylists()
from ls.c.

Rename addToStoredPlaylist() to spl_append_uri(), and remove the
clearStoredPlaylist() macro.

Renamed all public functions, prefix is "spl_".

No CamelCase in file names.

The list of commands is known at compile time.  Instead of creating a
linked list on startup, we can just register all commands in a static
sorted array.

The command pointers which are passed around aren't being modified -
in fact, no command pointer must be modified once it has been added to
the commandList.

No CamelCase and no struct typedefs.

client->permission is a bit set, and should be unsigned.

When adding a local file, clients have to use the "file" URI schema
described in RFC 1738 3.10.  By adding this schema to "urlhandlers", a
client can detect whether this feature is available.

The undocumented command "add /" adds the full music database to the
playlist.  Don't interpret this special path as a local file path.