Add DumpHeap tool.

This tool can take a textized full dump created via GDB commands as
documented here,
https://github.com/adamgreen/SmoothieCrashDumps#gathering-full-dump-to-send-for-analysis
and dump the allocations from the heap.  It does need to know where the
heap starts and ends.  The notes at the following URL talk about a way
to obtain these important heap addresses:
https://github.com/adamgreen/SmoothieCrashDumps/blob/master/issue93/Notes.creole