[BUILD] makefile now detects and uses git to set the version

[BUILD] makefile now detects and uses git to set the version

If git is found during the build process, then it will be used
to set the version, the commit number and the commit date. This
way, it will not be needed anymore to update the code to change
the version. The version is the last tag, and the commit number
is the number of commits since the last tag.