Pacify gcc -Wswitch-enum in bidi.c

Pacify gcc -Wswitch-enum in bidi.c

* src/bidi.c (bidi_get_type, bidi_resolve_explicit)
(bidi_find_bracket_pairs, bidi_resolve_brackets)
(bidi_resolve_neutral): Use ‘switch (INT_PROMOTE (E))’
to indicate that it’s intended that we not enumerate all the enum
values.

(cherry picked from commit 467a88394f8d7fe545bd236586a9a3ed991ab9dc)