The following is a list of symbols in libc_i18n that need to be replaced, because ON won't even build without them:
btowc
getwc
getws
fwide
mblen
putwc
wctob
wscol
isalnum
isalpha
isblank
iscntrl
isdigit
isgraph
islower
isprint
ispunct
isspace
isupper
_nl_langinfo
mbrtowc
mbsinit
isphonogram
_getwc
_putwc
fgetwc
fgetws
fputwc
fputws
towlower
towupper
mbrlen
mbtowc
wctomb
wctype
localeconv
nl_langinfo
regcomp
regexec
regfree
mbstowcs
isnumber
isspecial
mbsrtowcs
wcsrtombs
_scrwidth
wcsftime
wcstombs
wcswidth
strcoll
strfmon
strxfrm
isideogram
iswalpha
iswalnum
iswblank
iswcntrl
iswctype
iswdigit
iswgraph
iswlower
iswprint
iswpunct
iswspace
isxdigit
iswupper
setlocale
_tolower
tolower
_toupper
toupper
strftime
strptime
regerror
ungetwc
isenglish
fnmatch
wcscoll
wcrtomb
wcsxfrm
wctrans
towctrans
wcwidth
getdate
_getdate
mbst_get_lc_and_fp
_set_orientation_wide
iswxdigit
Yes, it's a lot.
