sample_muxer: Fixed bug with outputting audio cues.
sample_muxer: Fixed bug with outputting audio cues.

- For muxed content with default settings the cues was getting
  output on the audio track when it should be on the video track
  by default.
- Added check to command line parameter parsing to make sure
  there are enough parameters.
- If Cues are set to output on one type of track the other type
  is now disabled.

Change-Id: I96ef1978dc3f442f34364f6dee6cfb01571c7289

Suvarna1488/webm.libwebm,matanbs/webm.libwebm,Maria1099/webm.libwebm,felipebetancur/libwebm,gshORTON/webm.libwebm,jdm/libwebm,kleopatra999/webm.libwebm,felipebetancur/libwebm,abwiz0086/webm.libwebm,webmproject/libwebm,webmproject/libwebm,zofuthan/libwebm,reimaginemedia/webm.libwebm,webmproject/libwebm,zofuthan/libwebm,ericmckean/webm.libwebm,Acidburn0zzz/webm.libwebm,iniwf/webm.libwebm,pcwalton/libwebm,kalli123/webm.libwebm,kim42083/webm.libwebm