[pecoff] Implement ObjectFilePECOFF::GetDependedModules()

Summary:
This parses entries in pecoff import tables for imported DLLs and
is intended as the first step to allow LLDB to load a PE's shared
modules when creating a target on the LLDB console. 


Reviewers: rnk, zturner, aleksandr.urakov, lldb-commits, labath, asmith

Reviewed By: labath, asmith

Subscribers: labath, lemo, clayborg, Hui, mgorny, mgrang, teemperor

Differential Revision: https://reviews.llvm.org/D53094

llvm-svn: 348527