[Bug #20305] Fix matching against an incomplete character
When matching against an incomplete character, some `enclen` calls are
expected not to exceed the limit, and some are expected to return the
required length and then the results are checked if it exceeds.
Added by k0kubun (Takashi Kokubun) about 1 year ago
merge revision(s) 3a04ea2d0379dd8c6623c2d5563e6b4e23986fae: [Backport #20305]