* src/input/input_clock.c, include/input_ext-intf.h: introduced an i_pts_delay field in
input_thread_t (initialised to DEFAULT_PTS_DELAY).
* modules/access/*: i_pts_delay is now configurable on an access module basis. The pts
delay for http and mms have been raised to 4 * DEFAULT_PTS_DELAY, which is about 1.2
seconds worth of caching.