TTX: distinguish between fully-supported and hex tables

[n8willis]

The TTX format fully supports the

BASE, CBDT, CBLC, CFF, COLR, CPAL, DSIG, EBDT, EBLC, FFTM, GDEF,
GMAP, GPKG, GPOS, GSUB, JSTF, LTSH, MATH, META, OS/2, SING, SVG,
TSI0, TSI1, TSI2, TSI3, TSI5, TSIB, TSID, TSIJ, TSIP, TSIS, TSIV,
VDMX, VORG, avar, cmap, cvt, feat, fpgm, fvar, gasp, glyf, gvar,
hdmx, head, hhea, hmtx, kern, loca, ltag, maxp, meta, name, post,
prep, sbix, trak, vhea and vmtx

Tables. Other tables are dumped as hexadecimal data.

It might be helpful in the long run for fontfile-ttx-mode to treat these tables differently w.r.t. highlighting and linting.