[pvr.tvh] ignore mux packets when a channel switch is in progress
Revert "[pvr.tvh] a getDvrCutpoints response without a cutpoint list is not malformed,"

This reverts commit 063c21058ae175cd49c67620433778cb10fed8aa.
[pvr.tvh] remove unused m_started and m_startCond variables, relying on them
for the packet ignoring was obviously wrong
[pvr.tvh] reintroduce the "drop packets while switching channels" functionality
[pvr.tvh] ignore subscriptionStart if video stream details are missing

This fixes a bug where VAAPI sometimes crashes because we try to
initialize it with 0x0 video dimensions
[pvr.tvh] remove SChannel.now and SChannel.next, XBMC doesn't use
them and we needlessy trigger a lot of channel updates whenever
these values change
[pvr.tvh] bump version to 0.9.3