Fix Fleshstinger

[kphoenix137]

Yet another potentially controversial PR. This is also related to diasurgical/devilution#64 (comment)

As galaxyhaxz said, Split Skull Shield also had this same problem in the PR demo, where they used IPL_DUR instead of IPL_SETDUR, resulting in 5% increased durability, a very strange number to set, as it has absolutely no effect. Split Skull Shield was instead changed to have 15 durability, which is its base item durability in the PR demo (10), plus 5 (the original value set for IPL_DUR). This ended up making it a 1 durability nerf in retail, since they did not modify it to be 16 durability + 5 durability for whenever they buffed Buckler durability to 16.

Following this line of logic, I think an accurate assessment would be that Fleshstinger was intended to have +6 durability from the Long Bow durability at this time in development, not +6% durability (+6% durability results in a durability increase of 2. Like what??). Given that it's a Long Bow which in PR demo, had a durability of 20, the intent was likely for this bow to have instead 26 durability.

[FitzRoyX]

DUR and AC have no "add" power, so they figured let's just call it "DUR" instead of "DUR_AMP". It seems like that naming decision caused some confusion as people used DUR as if it meant ADD_DUR.

[AJenbo]

Please fix merge conflict