message: Fix compilation warning in thinblock_data_tests.cpp
  The warning was:
  warning: comparison between signed and unsigned integer expressions
  declaring `i` as uint32_t fixed the problem
diff: @@ -37,7 +37,7 @@ BOOST_AUTO_TEST_CASE(test_thinblockdata_stats1)
  {
  vector<int64_t> times1(1000); // minutes
  - for (int i = 0; i < times1.size(); i++)
  + for (uint32_t i = 0; i < times1.size(); i++)
  {
  times1[i] = 1000 * 60 * i;
  }
  