* src/audio_output/dec.c, include/aout_internal.h: the aout core was
automatically discarding audio samples that were above AOUT_MAX_ADVANCE_TIME
in the future. Problem is that p_input->i_pts_delay isn't a fixed value. We
now fetch this value from the input thread when we create an aout_instance_t.
This solves problems with the http access plugin.