waitress: Use standard socket buffer size

libav* uses its own HTTP implementation and the API calls do not benefit
from it anyway.
player: Fix state-machine

Song timer was shown without song playing.
Fix include guards

Macros starting with _ are reserved (see
http://www.gnu.org/software/libc/manual/html_node/Reserved-Names.html).
Fixes #440.
player: Add missing header for ffmpeg1.2

Closes #441.
Merge branch 'master' of https://github.com/PromyLOPh/pianobar