gj_utils: Add support for Homebrew-installed ID Utils.

Hi fcamel,

I notice that gj checks ID Utils with name "gid32" instead of "gid" on OSX. I guess this is the 32-bit executable name installed by MacPorts? With the one installed via up-to-dated Homebrew, it's compiled in 64-bit and is named just "gid." This change is to fix this and make gj works with Homebrew.

Thanks for your tool gain, GJ!

B.R.
Raphanus Lo