Replaces GLib's g_str_has_prefix().

mixramp_delay==nan() causes severe problems with cross-fading.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Use only ConfigData.hxx in plugin sources to reduce header
dependencies.

Look up top-level config options by enum (= integer), not by name
string.

When set, MPD will not auto-start playback on startup; it will be in
"paused" state.

Allocate a player_control object where needed, and pass it around.
Each "client" object is associated with a "player_control" instance.

This prepares multi-player support.

An '\n' was erroneously inserted in the line containing the state, e.g.
"state: \nplay" instead of "state: play".

Fix for bug #2992.

Use the functions song_save() and song_load() to use the same format
as in the database file for those songs which need the tags.

The only caller doesn't use its return value, and the value isn't
useful anyway.

Don't use a large stack buffer.

Let the C compiler concatenate string constants.