Handle set bonuses properly

[squeek502]

See nokka/d2s#5

The set bits correspond with how many items of that set need to be worn to get that bonus, and also with the values of the aprop fields in SetItems.txt.

If the bits are numbered 54321:

• If bit 1 is set, then it requires >= 2 items worn
• If bit 2 is set, then it requires >= 3 items worn
• If bit 3 is set, then it requires >= 4 items worn
• If bit 4 is set, then it requires >= 5 items worn
• If bit 5 is set, then it requires >= 6 items worn

Examples:

• M'avina's Belt

  • Set bonuses flag: 4 (00100)
  • SetItems.txt only has aprop3 field set
  • Only gets the bonus when >= 4 items are worn

• IK Armor

  • Set bonuses flag: 31 (11111)
  • SetItems.txt has aprop1-aprop5 fields set
  • Get a new bonus each additional item that is worn

• Trang's Armor

  • Set bonuses flag: 10 (01010)
  • SetItems.txt has aprop2 and aprop4 fields set
  • Only gets a new bonus when >= 3 items are worn and then another at >= 5 worn