Fixed bugs:

• Issue #238: (uname) on Windows 10 returns version 6.2

New features:

• change-file-timestamps! has been added.

Improvements:

• Creating symbolic link on MSYS2 checks 'MSYS' environment variable
• Creating symbolic link on Windows uses SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE if possible
• (archive) now also sets file timestamps