[Issue 24082] add Int128.toString that supports std.format

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24082

Nathan S. <n8sh.secondary at hotmail.com> changed:

           What    |Removed                     |Added
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            Summary|std.int128.Int128: add      |add Int128.toString that
                   |toString that supports      |supports std.format
                   |std.format                  |

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