Fix link access in ik fail log and add test code

[snozawa]

(irtmodel.l, test-irt-motion.l) : Fix link access in ik fail log and add test code for it.
This bug is reported in jsk-ros-pkg/jsk_roseus#139

Use :link for link access.
The accessor specification was discussed in
jsk-ros-pkg/jsk_model_tools#18 (comment)

[snozawa]

Travis failed because of this error:

$ sudo apt-get install -qq -y subversion gcc g++ libjpeg-dev libxext-dev libx11-dev libgl1-mesa-dev libglu1-mesa-dev libpq-dev libpng12-dev xfonts-100dpi xfonts-75dpi msttcorefonts

Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/u/update-notifier/update-notifier-common_0.119ubuntu8.6_all.deb 404 Not Found [IP: 2001:67c:1562::14 80]

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

The command "sudo apt-get install -qq -y subversion gcc g++ libjpeg-dev libxext-dev libx11-dev libgl1-mesa-dev libglu1-mesa-dev libpq-dev libpng12-dev xfonts-100dpi xfonts-75dpi msttcorefonts" failed and exited with 100 during .

It says apt-get update is missing.
I'll try to fix this.

[snozawa]

I fixed this problem through #102.
I updated this PR and restarted travis.