add new makefile environment variable UPLOAD_UTILITY
add new makefile environment variable UPLOAD_UTILITY

this adds a new make file environment variable UPLOAD_UTILITY that
provides the name of the application to be used to upload a binary
executable to the target device.

prpplague/Userspace-Arduino,prpplague/Userspace-Arduino,prpplague/Userspace-Arduino,bugobliterator/BUAGI,bugobliterator/BUAGI,bugobliterator/BUAGI,bugobliterator/BUAGI,bugobliterator/BUAGI,prpplague/Userspace-Arduino,bugobliterator/BUAGI