[lldb] Read modules from memory when a local copy is not available

Summary:
When the local lldb doesn't have access to a copy of the modules in the target, e.g. winphone, with this change now we read these modules from memory.

There are mainly 2 changes:
1. create pecoff object files from memory
2. read from memory when the local file is not available

Reviewers: sas, fjricci, zturner

Subscribers: #lldb

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D24284

llvm-svn: 284422