COmpilation problems with older Freetype 2

[Vincent Béron]

A patch by Huw broke compilation of Wine on RH8 (and probably other
platforms as well) which use Freetype 2.1.3 or earlier. More
specifically, FT_ENCODING_NONE is undefined.

Other ft_encoding_* (or FT_ENCODING_*) problems have arised in the past,
but the solution used identifiers already present in older Freetype
versions.

The attached patch works (and results in the same compiled code IMHO),
but looks like a hack rather than a proper fix (use MS_MAKE_TAG? that
has already been removed in the past to use ft_encoding_*).

Vincent