Makefile.dep: include board specific application dependency file
Makefile.dep: include board specific application dependency file

This commit allows to add a Makefile.dep file in an application directory to finely tune application dependencies, based on a board.
Using this mechanism, if an application has dependencies pulled-in based on a board, info-boards-supported, will take this into account to determine the boards supported by an application

jasonatran/RIOT,smlng/RIOT,yogo1212/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,basilfx/RIOT,kaspar030/RIOT,ant9000/RIOT,miri64/RIOT,smlng/RIOT,basilfx/RIOT,basilfx/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,miri64/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,ant9000/RIOT,authmillenon/RIOT,yogo1212/RIOT,mtausig/RIOT,x3ro/RIOT,authmillenon/RIOT,aeneby/RIOT,toonst/RIOT,smlng/RIOT,yogo1212/RIOT,miri64/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,kaspar030/RIOT,mtausig/RIOT,josephnoir/RIOT,yogo1212/RIOT,OTAkeys/RIOT,smlng/RIOT,OlegHahm/RIOT,jasonatran/RIOT,x3ro/RIOT,kaspar030/RIOT,authmillenon/RIOT,x3ro/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,miri64/RIOT,smlng/RIOT,x3ro/RIOT,josephnoir/RIOT,mtausig/RIOT,toonst/RIOT,ant9000/RIOT,toonst/RIOT,mtausig/RIOT,kaspar030/RIOT,authmillenon/RIOT,aeneby/RIOT,toonst/RIOT,yogo1212/RIOT,kYc0o/RIOT,aeneby/RIOT,aeneby/RIOT,miri64/RIOT,authmillenon/RIOT,basilfx/RIOT,ant9000/RIOT,OlegHahm/RIOT,josephnoir/RIOT,kYc0o/RIOT,toonst/RIOT,RIOT-OS/RIOT,aeneby/RIOT,jasonatran/RIOT,x3ro/RIOT,mtausig/RIOT,jasonatran/RIOT,authmillenon/RIOT,OlegHahm/RIOT,kYc0o/RIOT,basilfx/RIOT,josephnoir/RIOT