A conditional originally added to shield_add_strength() to make shields not recharge beyond the recharge limit forgot to check that the amount shields are changing by was positive (unlike a couple other conditionals added/modified around the same time), so a call to shield_add_strength() with a negative delta (e.g. when transferring energy from shields to weapons) when the current shield strength is at or above the recharge limit (i.e. full strength when a recharge limit isn't specified) would immediately return without doing anything. This would, of course, result in no change to shield strength... so if you had full shields and had drained your weapon batteries dry, you could get free energy by hitting the button to transfer energy from your shields.
This introduces a new mechanism for handling bit flags. Instead of using an int (or two, or three) to write bits into, this uses the std::bitset in a wrapper class that accepts an enum class as input. This means that certain classes of errors we've had a few of in the engine, where a coder used the wrong set of flags or checked them against the wrong variable (SF_STEALTH vs SIF_STEALTH, for example) can now be detected at a compiler level rather than not at all.
MageKing17