Fix langtag parsing

Julien LepillerWed Apr 01 03:28:17+0200 2020

e4fcd88

guile-rdf/rdf
namelast commitdate
rdf.scmInitial commitTue Mar 31 04:36:06+0200 2020
xsd.scmInitial commitTue Mar 31 04:36:06+0200 2020