Implement channel order mapping

[gavv]

For #86.

Before this commit, order of channels in surround layout was defined by ChannelPosition enum values.

After this commit, each ChannelSet (and hence SampleSpec) contains ChannelOrder enum, which defines order of surround channels in memory.

Currently two orders are supported:

• ChanOrder_Smpte - widely used order define by ITU/SMPTE spec; compatible with Dolby, AIFF-C, AAC, and RTP/AVP
• ChanOrder_Alsa - order used by ALSA hw devices

ChannelMapper now takes order into account. If input & output orders differ, it automatically performs reordering.

So far surround layouts were not exposed in API and CLI. Thus, changing default order did not break anything, however all tests had to be updated to match new order.

[dshil]

Hi @gavv, I would suggest to simplify setup_map_matrix_().
The following things complicate the understanding of the code base:

• for loop contains more then one variable:

  for (size_t in_index = 0, n_ord = 0; in_order.chans[n_ord] != ChanPos_Max; n_ord++) {}
  for (size_t n = 0; !ch_map && n < ROC_ARRAY_SIZE(chan_maps); n++) {}

• for loop exit condition should be calculated somehow:

  for (size_t in_index = 0, n_ord = 0; in_order.chans[n_ord] != ChanPos_Max; n_ord++) {}

• Repeating code for output and input channels

• Nested constructions:

  map_matrix_[out_index_map[ch]][in_index_map[ch]] = 1.f;
  roc_panic_if_not(out_index_map[ch] < ChanPos_Max
               && in_index_map[ch] < ChanPos_Max);

It can be done after the PR. Suggested patch

[dshil]

I'll add the suggested patch in a separate PR.