overlap string and bytes features

[mr-tz]

for 5a2f620f29ca2f44fc22df67b674198f

I think we should not extract byte features for obvious string references, see e.g.:

  insn: 0x40C7CC: bytes(46 72 65 73 68 46 54 50 00 2E 53 4D 46 00 42 6C 61 7A 65 46 74 70 00 73 69 74 65 2E 64 61 74 00 4C 61 73 74 50 61 73 73 77 6F 72 64 00 4C 61 73 74 41 64 64 72 65 73 73 00 4C 61 73 74 55 73 65 72 00 4C 61 73 74 50 6F 72 74 00 53 6F 66 74 77 61 72 65 5C 46 6C 61 73 68 50 65 61 6B 5C 42 6C 61 7A 65 46 74 70 5C 53 65 74 74 69 6E 67 73 00 5C 42 6C 61 7A 65 46 74 70 00 2E 66 70 6C 00 46 54 50 2B 2B 2E 4C 69 6E 6B 5C 73 68 65 6C 6C 5C 6F 70 65 6E 5C 63 6F 6D 6D 61 6E 64 00 47 6F 46 54 50 00 43 6F 6E 6E 65 63 74 69 6F 6E 73 2E 74 78 74 00 33 44 2D 46 54 50 00 73 69 74 65 73 2E 69 6E 69 00 5C 33 44 2D 46 54 50 00 5C 53 69 74 65 44 65 73 69 67 6E 65 72 00 53 4F 46 54 57 41 52 45 5C 43 6C 61 73 73 65 73 5C 54 79 70 65 4C 69 62 5C 7B 46 39 30 34 33 43 38 38 2D 46 36 46)
  insn: 0x40C7CC: mnemonic(push)
  insn: 0x40C7CC: string(FreshFTP)

where 46 72 65 73 68 46 54 50 -> FreshFTP