devel/root: Update to 6.38/00

New port options:
FFTW3 (OFF), GEOM (ON), UNFOLD (ON)

Renamed port options (now using same namings as upstream):
FITS->FITSIO, TMLP->MLP, TMVAML->TMVA

Removed port options (following upstream):
MYSQL, PGSQL

In addition, MATHMORE is no longer a default option.
It has otherwise been a default option in the ports tree until
now, unlike upstream.

ChangeLog: https://root.cern/doc/v638/release-notes.html
PR: 291434