Updating files for CHL 1.31.1

[DaloLorn]

Porting a few recent Highlander submissions (primarily mine, but also anyone else who touched the relevant CHL files) to LWotC.

• Commit f749775 updates XMB's custom hitcalcs to support the OverrideCoverLevel feature.
• Commit 418cdf7 updates the built-in PI ShotHUD to respect and implement the PREVIEW_ARMOR_MITIGATION config.
• Commit 99005bb brings X2Effect_ApplyAltWeaponDamage in sync with all new CHL features added to its parent class.
  • This is the only commit I haven't rigorously tested over the past several months. While I have previously transplanted my AdjustArmorMitigation and OverrideDefenseBypass changes to this file and tested that, there have been a few amendments (and a few new features by other contributors) in the interim, and I have not retested since making the updates in this commit.

(Yay, I might finally be able to play TJ without having my dev builds clobber its configs...)