Correct 4.3 to reference the 2010 version of SMPTE-TT for IMSC compliance

[wilaw]

[Filed on behalf of Pierre-Anthony Lemieux]

On page 153, DASH-IF IOP 4.3 recommends the use of IMSC, and
(informatively) references the 2013 version of SMPTE-TT (ST
2052-1:2013) as a subset of IMSC.

IMSC references the 2010 version of SMPTE-TT (ST 2052-1:2010).

Unfortunately the 2013 version of SMPTE-TT introduces (perhaps
inadvertently) incompatibilities with IMSC (not in functionality but
in namespace identifier).

In the short-term, it might be best to correct DASH-IF IOP to
reference the 2010 version of SMPTE-TT -- since the objective is to
converge on IMSC.

In the long-term, SMPTE should fix the issue above.

[palemieux]

@wilaw Thanks!