Petr Mrázek 1868e0ccf1 GH-3229 fix copy seed button not working for newer worlds

Added the `optional-bare` library and refactored NBT reading
code to support this change.

2021-02-06 15:58:03 +01:00

optional bare

A simple single-file header-only version of a C++17-like optional for default-constructible, copyable types, for C++98 and later.

Imported from: 0bb1d183bc