i#5411 bbdup mem: Eliminate per-block bookkeeping for no-dup usage

Augments drbbdup to allow a value of 0 for drbbdup_options_t.non_default_case_limit. When it is set to 0, no duplication will occur, and no per-block data structures will be allocated, saving memory.

Adds a test case for this.

Updates drmemtrace to use this when multi-case options are not selected.

Sanity test: Before:

  $ bin64/drrun -rstats_to_stderr -t drcachesim -offline -max_global_trace_refs 10K -- ~/spec2006/bzip2-test/bzip2_base.gcc-64bit ~/spec2006/bzip2-test/dryer.jpg 2
                Peak vmm blocks for unreachable heap :               747
              Peak vmm virtual memory in use (bytes) :           6963200

After:

                Peak vmm blocks for unreachable heap :               631
              Peak vmm virtual memory in use (bytes) :           6389760

Along with the prior shift to use unreachable heap for per-block data and then to eliminate and improve per-thread data, this concludes the memory reductions for #5411 (closed).

Fixes #5411 (closed)