Move symtab.* to topology/

- Adapt #includes and some minor cleanup in touched files.
- Convert symtab.c to C++ to get rid of a "macros.h" dependency, and
  clean up the includes otherwise as well.
- Adjust valgrind memory leak suppression to suppress on an extern "C"
  function.

This new subdirectory is an initial home for everything related to basic
topology and index group handling.  More files will follow.

Change-Id: Id5b1a626ef4a90836f70a8b4c7f24ff52c768a5d