MFC rev. 1.37: Never zero-out db_last_symtab. Whan backtraces are done in parallel in several threads, one symbol lookup could clear db_last_symtab when another one going to use it as starting point for traversal.
MFC rev. 1.37:
Never zero-out db_last_symtab. Whan backtraces are done
in parallel in several threads, one symbol lookup could
clear db_last_symtab when another one going to use it as
starting point for traversal.

Approved by:	pjd (mentor)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase