ddsperf enhancements

* per-thread CPU usage (only those threads where the load is over 0.5%,
  if the sum of threads below that threshold exceeds 0.5%, it prints an
  aggregate for those threads);

* also report RSS;

* network load (only on request, as percentage of specified network
  bandwidth and actual bytes in/out, with the output suppressed if it is
  0%);

* publish CPU usage so a ddsperf instance can display CPU loads for
  its peers;

* handle SIGXFSZ (file size exceeded) by displaying one last line of
  statistics before killing itself; this simply a debugging tool to make
  it easier to get a trace covering a high sample-rate start-up issue;

* default topic changed to "KS" because that allows all the options to
  be used, this has a negative impact on performance (both latency and
  small-sample throughput) but it should be less surprising to users;

* specifying a size is now done by appending "size N" (where N is the
  size in bytes) after a "ping" or "pub" command, rather than it having
  to set it via a command-line option;

Note that some of this is platform-dependent -- SIGXFSZ is currently
only on Linux and macOS, and CPU and network load reporting is currently
only on Linux, macOS and Windows.

Signed-off-by: Erik Boasson <eb@ilities.com>

src/tools/ddsperf/CMakeLists.txt

@@ -11,7 +11,7 @@
 #
 
 idlc_generate(ddsperf_types ddsperf_types.idl)
-add_executable(ddsperf ddsperf.c)
+add_executable(ddsperf ddsperf.c cputime.c cputime.h netload.c netload.h)
 target_link_libraries(ddsperf ddsperf_types ddsc)
 
 if(WIN32)