fix Lua 5.1 library detection failed on Gentoo and derivatives

closes #6529
Merge pull request #6782 from Mailaender/configure-gentoo

Fixed Lua 5.1 library detection failed on Gentoo and derivatives
Define BaseLine offset for ButtonWidget.
Allow custom ScrollPanel button styles.
Split out TS’s dropdowns.yaml.
Overhaul the replay sidebar.
Add a new stats button glyph.
Add the statistics button to TD replays.