[XCOFF]implement parsing relocation information for 32-bit xcoff object file

Summary:
    Parsing the relocation entry information for 32-bit xcoff object file
including deal with the relocation overflow.

Reviewers: hubert.reinterpretcast, jasonliu, sfertile, xingxue.

Subscribers: hiraditya, rupprecht, seiya

Differential Revision: https://reviews.llvm.org/D67008

llvm-svn: 374946