Introduce VERCMD in Makefile
Introduce VERCMD in Makefile

This is useful when the author has to make a release commit, in which
case `make doc` is required, but, because the tag doesn't exist yet, the
output of VERCMD won't be what we want. Therefore, we need to override
VERCMD for the *doc* target: `make VERCMD=false doc`.

medisun/bspwm,medisun/bspwm,medisun/bspwm