Expose client version information in non-debug builds (luanti-org#15708)

Co-authored-by: SmallJoker <SmallJoker@users.noreply.github.com>
Co-authored-by: Lars Mueller <appgurulars@gmx.de>
Co-authored-by: sfan5 <sfan5@live.de>

Don't memset SEvent directly (luanti-org#15359)

Fixes a compiler warning by manually zeroing the tag and the largest union member instead

Bump version to 5.8.1