libvisio license change

[David Tardon]

Hello all,

libvisio changed license from GPL 2+ / LGPL 2.1+ / MPL 1.1 to MPL 2.0 in
0.1.0 (built for Rawhide today).

AFAIK the users of libvisio in Fedora are calligra, inkscape,
libreoffice and writerperfect.

D.