Object/Minidump: Add support for the ThreadList stream

Summary:
The stream contains the list of threads belonging to the process
described by the minidump. Its structure is the same as the ModuleList
stream, and in fact, I have generalized the ModuleList reading code to
handle this stream too.

Reviewers: amccarth, jhenderson, clayborg

Subscribers: llvm-commits, lldb-commits, markmentovai, zturner

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61064

llvm-svn: 359762