Tracedump: Add public library symbols (exports) to dump symbol table

Demangle and append each library func/data export to the dump. Gives
slightly better backtraces in trace dumps.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Calle Wilund <calle@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>