libxdmcp6-dbg software package provides X11 authorisation library (debug package), you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install libxdmcp6-dbg
libxdmcp6-dbg is installed in your system.
Make ensure the libxdmcp6-dbg package were installed using the commands given below,
$ sudo dpkg-query -l | grep libxdmcp6-dbg *
You will get with libxdmcp6-dbg package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Library development |
| Package | libxdmcp6-dbg |
| Version | 1:1.1.1-1 |
| Description | X11 authorisation library (debug package) |
| Sub Section | libdevel |