build/ansible: adding mathgl package, requested by Diego Sejas Viscarra
build/ansible: adding mathgl package, requested by Diego Sejas Viscarra

DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,sagemathinc/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc