[Bug c/107954] Support -std=c23/gnu23 as aliases of -std=c2x/gnu2x

[lukaszcz18 at wp dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107954

Jamaika <lukaszcz18 at wp dot pl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lukaszcz18 at wp dot pl

--- Comment #2 from Jamaika <lukaszcz18 at wp dot pl> ---
I shouldn't be writing as an outsider.
I don't know what c2x accepts.
For gcc 11.3.1 and c++20 I am forced to use c2x.
For example, compiling HTJ2K grok c++20 and zlib shows that zlib does not
conform to c++20 standards and some functions are deprecated.

adler32.c: In function 'adler32_z':
adler32.c:63:15: warning: old-style function definition
[-Wold-style-definition]
   63 | uLong ZEXPORT adler32_z(adler, buf, len)
      |               ^~~~~~~~~
adler32.c: In function 'adler32':
adler32.c:134:15: warning: old-style function definition
[-Wold-style-definition]
  134 | uLong ZEXPORT adler32(adler, buf, len)
      |               ^~~~~~~
adler32.c: In function 'adler32_combine_':
adler32.c:143:13: warning: old-style function definition
[-Wold-style-definition]
  143 | local uLong adler32_combine_(adler1, adler2, len2)
      |             ^~~~~~~~~~~~~~~~
adler32.c: In function 'adler32_combine':
adler32.c:172:15: warning: old-style function definition
[-Wold-style-definition]
  172 | uLong ZEXPORT adler32_combine(adler1, adler2, len2)
      |               ^~~~~~~~~~~~~~~
adler32.c: In function 'adler32_combine64':
adler32.c:180:15: warning: old-style function definition
[-Wold-style-definition]
  180 | uLong ZEXPORT adler32_combine64(adler1, adler2, len2)
      |               ^~~~~~~~~~~~~~~~~
compress.c: In function 'compress2':
compress.c:22:13: warning: old-style function definition
[-Wold-style-definition]
   22 | int ZEXPORT compress2(dest, destLen, source, sourceLen, level)
      |             ^~~~~~~~~
compress.c: In function 'compress':
compress.c:68:13: warning: old-style function definition
[-Wold-style-definition]
   68 | int ZEXPORT compress(dest, destLen, source, sourceLen)
      |             ^~~~~~~~
compress.c: In function 'compressBound':
compress.c:81:15: warning: old-style function definition
[-Wold-style-definition]
   81 | uLong ZEXPORT compressBound(sourceLen)
      |               ^~~~~~~~~~~~~
crc32.c: In function 'byte_swap':
crc32.c:126:16: warning: old-style function definition [-Wold-style-definition]
  126 | local z_word_t byte_swap(word)
      |                ^~~~~~~~~
crc32.c: In function 'multmodp':
crc32.c:551:15: warning: old-style function definition [-Wold-style-definition]
  551 | local z_crc_t multmodp(a, b)
      |               ^~~~~~~~
crc32.c: In function 'x2nmodp':
crc32.c:575:15: warning: old-style function definition [-Wold-style-definition]
  575 | local z_crc_t x2nmodp(n, k)
      |               ^~~~~~~
crc32.c: In function 'crc_word':
crc32.c:726:15: warning: old-style function definition [-Wold-style-definition]
  726 | local z_crc_t crc_word(data)
      |               ^~~~~~~~
crc32.c: In function 'crc_word_big':
crc32.c:735:16: warning: old-style function definition [-Wold-style-definition]
  735 | local z_word_t crc_word_big(data)
      |                ^~~~~~~~~~~~
crc32.c: In function 'crc32_z':
crc32.c:748:23: warning: old-style function definition [-Wold-style-definition]
  748 | unsigned long ZEXPORT crc32_z(crc, buf, len)
      |                       ^~~~~~~
crc32.c: In function 'crc32':
crc32.c:1072:23: warning: old-style function definition
[-Wold-style-definition]
 1072 | unsigned long ZEXPORT crc32(crc, buf, len)
      |                       ^~~~~