[llvm-readobj] Add support for MachO DataInCodeDataCommand.

Example output:

File: <stdin>
Format: Mach-O arm
Arch: arm
AddressSize: 32bit
DataInCode {
  Data offset: 300
  Data size: 32
  Data Regions [
    DICE {
      Index: 0
      Offset: 0
      Length: 4
      Kind: 1
    }
    DICE {
      Index: 1
      Offset: 4
      Length: 4
      Kind: 4
    }
    DICE {
      Index: 2
      Offset: 8
      Length: 2
      Kind: 3
    }
    DICE {
      Index: 3
      Offset: 10
      Length: 1
      Kind: 2
    }
  ]
}

Differential Revision:	 http://reviews.llvm.org/D12084

llvm-svn: 245732