Fix man page substitutions

See merge request xorg/lib/libxcvt!2

Fills in version & section info in cvt.1 and fixes meson warning:
man/meson.build:4: WARNING: The variable(s) 'appmansuffix', 'filemansuffix', 'vendorversion' in the input file 'man/cvt.man' are not present in the given configuration data.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

readme: Project has moved

See merge request xorg/lib/libxcvt!1

Project has moved under the xorg/lib namespace, update the instructions
accordingly.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>