Import ROOT directly, alias gbl to ROOT
As discussed on MM; this makes using ROOT features such as ROOT.Numba easier, as they are only accessible through import ROOT
rather than from cppyy import gbl as ROOT
.
I'm not sure what exactly the check for 6.18 was for; I left the check for ><6.22 as the handling of command line options was changed with the new pyROOT.
EDIT: AFAIU, the check for 6.18 is moot if we're importing directly as import ROOT
Edited by Sebastien Wertz