Adding SIL Open Font License "liberation fonts"

Hi all,

These fonts are based on "croscore fonts". They're licensed under the
SIL OFL v1.1: https://opensource.org/licenses/OFL-1.1

The restriction on font names is a common restriction for fonts.
It is otherwise a copyleft-ish license. If you modify it, you must
change the name and use the same license.

I'd like to discuss this mostly because it is a new license.

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The diff for adding them: http://coypu.sdf.org/liberation.diff
(+cvs import to xsrc/external/ofl/font-liberation-ttf/dist
 + adding generated ttf files via pkgsrc build to
                xsrc/external/ofl/font-liberation-ttf/src )

These fonts are 4.3M (TTF files) and quite good. They are metric
compatible with common Windows fonts.