OSV-2020-1834 Stack-buffer-overflow in onigenc_unicode_get_case_fold_codes_by_str

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25893 Crash type: Stack-buffer-overflow WRITE 4 Crash state: onigencunicodegetcasefoldcodesbystr utf16begetcasefoldcodesbystr unravelcasefoldstring...