We currently always build tcmalloc.o which doesn't enable the debugging support in tcmalloc, but we could easily enable those features by compiling debugallocation.o instead (which includes tcmalloc.o). We could either always do this when building with --dbg=on, or we could create a new option for the --allocator flag, probably --allocator=tcmalloc-debug.

We need to double check that tcmalloc's internal valgrind detection and avoidance is functioning correctly.