INES Mapper 115

Additionally, some games assigned as mapper 248 (such as Bao Qing Tian) should be emulated with this mapper 115.

 Here are Disch's original notes:  
 ========================
 =  Mapper 115          =
 ========================
 
 Example Game:
 --------------------------
 Yuu Yuu Hakusho Final - Makai Saikyou Retsuden
 
 
 Notes:
 ---------------------------
 MMC3 variant.  For info on MMC3, see mapper 004.
 
 Regs at $6000-7FFF means no PRG-RAM
 
 
 Registers:
 ---------------------------
 
 Range,Mask:   $6000-7FFF, $6001
 
   $6000:  [O... PPPP]
     O = PRG Mode
     P = 16k PRG Page
 
   $6001:  [.... ...C]
     C = CHR Block select
 
   $8000-FFFF:  Same as MMC3
 
 
 CHR Setup:
 ---------------------------
 
  'C' selects a 256k CHR block for all the CHR selected by the MMC3.  You can think of this as a CHR-OR of
 $000 or $100 depending on 'C'.
 
 
 PRG Setup:
 ---------------------------
 
        $8000   $A000   $C000   $E000  
       +-------------------------------+
 O=0:  |              MMC3             |
       +-------------------------------+
 O=1:  |     $6000     |     MMC3      |
       +---------------+---------------+
 
 Normal MMC3 PRG setup applies.  If the O mode bit is set, then $8000-BFFF no longer reflects the typical MMC3
 setup, and instead has a 16k page selected by $6000.