I wrote a script for helping myself to install GDL when I'm using a computer which I don't own (and I cannot install the *-dev packages of GNU/Linux distribution). It is really a bit hard to take care of all the dependencies, IMHO.
The script is not perfect yet, but it works for me and probably I'll dedicate it more time in the future. Maybe you find it useful also.
It is the file installing_last_version_of_gdl.sh that you can find here
The rest of the files are IDL code of a taken course of Image Manipulation. Maybe you can find them useful also.