Import v20141206, Merge true color extension

Import v20141201, add support for high-compression mode

Import v20141109, Support PBM image format, Cherry-picked 2c58382

Import v20141109, Support PBM image format

Import sixel-tc (true color version) v20141107

Follow updates of original distribution 2014-10-05

Import from http://nanno.dip.jp/softlib/man/rlogin/sixel.tar.gz