P2460 Relax requirements on wchar_t to match existing practices

[wg21bot]

P2460R0 Relax requirements on wchar_t to match existing practices (Corentin Jabot)

[tahonermann]

SG16 discussed P2460R0 during its 2021-10-06 telecon. The following poll was taken:

• Poll 1: Add expanded motivation to D2460R0 and forward the paper so revised to EWG
  with a recommended ship vehicle of C++23.

  • Attendance: 10

    SF	F	N	A	SA
    5	3	1	0	0

  • Strong consensus in favor.

This paper is now ready for review by EWG and LEWG.

Review by EWG is necessary because this paper relaxes current core language restrictions.

Review by LEWG is necessary because this paper transfers the prior core language restrictions to library functions that accept a wide string. This paper arguably introduces a new form of library UB because a library function accepting a wide string may now encounter a wide string for which some code units of the string do not directly encode a character (e.g., a code unit could now specify a UTF-16 surrogate).

[brycelelbach]

A Library Evolution motion was made to advance this paper directly to electronic polling on 2021-10-31. The motion passed.