Feature or enhancement

(A clear and concise description of your proposal.)

memchr is currently used ifsizeof(STRINGLIB_CHAR) == sizeof(char) because it faster
than the standard C loops alternatives.

wmemchr has often roughly the same performance asmemchr and can be used
in the same way asmemchr to speedup some of the string functionsSTRINGLIB(find_char)
andSTRINGLIB(replace_1char_inplace) are the two easiest candidates.

Pitch

(Explain why this feature or enhancement should be implemented and how it would be used.
Add examples, if applicable.)

It would, in some instances, makewide_str.find(wide_str_of_len_one) faster.

Previous discussion

The idea was discussed a bit in#69009 but wasn't the main topic of the issue
or put into any patches.