OS_Mop, Open memory (allocate memory pool)

IN:
     A = memory mask arguments (several arguments OR'ed together):

          Destination segment (allocated memory addressed for segment):
          MM_S0 ($00), segment 0
          MM_S1 ($40), segment 1
          MM_S2 ($80), segment 2
          MM_S3 ($C0), segment 3

          Source of memory (to be allocated):
          MM_FIX ($02), fixed workspace (not subject to swapping)
          MM_SLT ($04), explicit slot usage
          MM_EXC ($10), exclusive use of bank
          MM_MUL ($20), use multiple banks

     B = 0, always
     C = bank or slot number if MM_SLT = 1 and MM_MUL = 0
		  MC_AS ($00), find an exclusive bank in any slot
          MC_CI ($10), internal memory
          MC_C1 ($01), card 1
          MC_C2 ($02), card 2
          MC_C3 ($03), card 3
		  or ($20-$ff), explicit bank

OUT, if call successful:
     Fc = 0
     IX = memory pool handle
OUT, if call failed:
     Fc = 1
     A = error code:
          RC_NA ($06), handle not available
          RC_ROOM ($07), no room

Registers changed after return:
     A.FBCDEHL/..IY same
     .F......./IX.. different