Contrary to the PCL5 Developer's Guide, the ascenders in TFM files

Contrary to the PCL5 Developer's Guide, the ascenders in TFM files
can be negative also.

* src/utils/hpftodit/hpftodit.cc (char_info): `ascent' must be
`int16'.
(read_char_table): Avoid negative ascenders.
(output_charset): Add cast.
* font/devlj4/*: Regenerated.

Replace unnamed glyphs for DVI fonts with `uXXXX' glyph names where
possible.

* font/devdvi/generate/{tc,texttt,ec,texmi,texsy,textex}.map: Do it.
* font/devdvi/generate/textex.map: Map glyph 23 to `u21C6' instead
of `<>'.
* font/devdvi/*: Regenerated.

Map `la' and `ra' to U+27E8 and U+27E9.  These two characters have
normal width, while the previously used characters (U+2329 and
U+232A) are classified as wide due to canonical equivalence with the
CJK punctuation characters U+3008 and U+3009.

* font/devutf8/R.proto: Updated.
* src/roff/troff/uniglyph.cc, src/roff/troff/glyphuni.cc: Ditto.

* man/groff_char.man: Simplify handling of table traps by
introducing `start block' and `end block' macros.
(Ns, Ne, 2s, 2e, Ds, De): New macros.
(DL): Make it work with Unix troff also.
Fix code values of `la' and `ra'.

* tmac/dvi.tmac: Define `<>' for CW and CWI.