Less overhead than fetch_and() for what we do.

Fixes segmentation fault.

If END is omitted, mpd should use the highest possible value instead of raising an error.
This partially reverts 52e9cab1

Workaround for driver bug observed on the Raspberry Pi, see code
comment for details.

Fixes nullptr dereference in std::string::operator=().  Also fixes a
memory leak by using config_get_block_string() instead of
config_dup_block_string().

Fixes assertion failure.

Would require gcc 4.7, and MPD attempts to be compatible with gcc 4.6.

When all outputs fail, MPD automatically pauses playback, but did not
emit the IDLE_PLAYER event.  Thus, clients were not woken up.  (Mantis
3665)