[Nucleo] Nucleo dependencies

[Nicolas Roussel]

Hi,

> while trying to clean metisse dependencies, I discovered nucleo is  
> trying to pull exif as a build dependencies but there is no code at  
> all
> in nucleo using libexif.

nucleo/image/encoding/JPEG.cxx uses libexif to figure out the  
orientation of JPEG images and automatically rotate them.

docs/installation.html lists nucleo's dependencies. As it says,  
OpenGL (AGL or GLX), libjpeg, libexif, libpng, freetype2 and dns-sd  
will be used if available at compilation time. But nucleo should  
compile fine without them.

Among these, I think OpenGL is the only one you really need to build  
the Metisse compositor. You'll need libjpeg if you want to be able to  
take screenshots, though.

As a Mac user relying on Fink for libs that are not part of a  
standard OS X installation, I tend to think twice before adding a new  
dependency. libexif seemed small and stable enough to me. Have you  
had any problem with it?

I could probably replace libjpeg, libpng and libexif with a single  
image manipulation library. Suggestions are welcome.

One last thing: I will soon commit some files that add basic XMPP  
support to nucleo. This code uses expat to parse XML and gnutls for  
secured communications. More optional dependencies...

Nicolas