This adds new SB API calls and classes to allow a user of the SB API to obtain a full list of memory regions accessible within the process. Adding this to the API makes it possible use the API for tasks like scanning memory for blocks allocated with a header and footer to track down memory leaks, otherwise just inspecting every address is impractical especially for 64 bit processes.
These changes only add the API itself and a base implementation of GetMemoryRegions() to lldb_private::Process::GetMemoryRegions.
I will submit separate patches to fill in lldb_private::Process::GetMemoryRegionInfoList and GetMemoryRegionInfo for individual platforms.
The original discussion about this is here: