Implement GetMemoryRegions() for Linux and Mac OSX core files.

Summary:
This patch fills in the implementation of GetMemoryRegions() on the Linux and Mac OS core file implementations of lldb_private::Process (ProcessElfCore::GetMemoryRegions and ProcessMachCore::GetMemoryRegions.) The GetMemoryRegions API was added under: http://reviews.llvm.org/D20565

The patch re-uses the m_core_range_infos list that was recently added to implement GetMemoryRegionInfo in both ProcessElfCore and ProcessMachCore to ensure the returned regions match the regions returned by Process::GetMemoryRegionInfo(addr_t load_addr, MemoryRegionInfo &region_info).

Reviewers: clayborg

Subscribers: labath, lldb-commits

Differential Revision: http://reviews.llvm.org/D21751

llvm-svn: 274741