Fixed a few bugs in IRMemoryMap:

- If an allocation is mirrored between the host
  and the process, update the host's version
  before returning a DataExtractor pointing to
  it.

- If anyone attempts to access memory in a
  process/target that does not have a corresponding
  allocation, try accessing the memory directly
  before erroring out.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@179561 91177308-0d34-0410-b5e6-96231b3b80d8