IC bug fix: add_tile/get_tile not peroperly honoring chend < chbegin (#2742)
IC bug fix: add_tile/get_tile not peroperly honoring chend < chbegin (#2742)

For IC::add_tile() and IC::get_tile(), the documentation advertised that
passing chend < chbegin meant "all channels". But the implementation was
setting chend=nchannels but not setting chbegin to 0.

Signed-off-by: Larry Gritz <f0a1ce6f80112d72f7276457fd261d671b827567@larrygritz.com>
OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio