message: Prometheus format fixes
  replace '-' with '_'
  add PROM_EOL (\n) for prom output
diff: @@ -67,6 +67,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  #include "threadpool.h"
  std::string const HTTP_EOL( "\r\n" );
  +std::string const PROM_EOL( "\n" );
  class Indent {
  public:
  @@ -678,9 +679,13 @@ private:
  }
  }
  - std::string replaceSpaceWithUnderbar( std::string const& s ) {
  + std::string replaceIllegalCharsWithUnderbar( std::string const& s ) {
  size_t pos = 0;
  std::string str(s);
  + while ( ( pos = str.find( '-', pos ) ) != std::string::npos ) {
  + str.replace( pos, 1, "_" );
  + }
  + pos = 0;
  while ( ( pos = str.find( ' ', pos ) ) != std::string::npos ) {
  str.replace( pos, 1, "_" );
  }
  @@ -722,7 +727,7 @@ private:
  template <typename Counter>
  void PrometheusPrinter::printCounter( std::string const & name, Counter c ) {
  - ss << replaceSpaceWithUnderbar(name) << printHierarchy() << c << HTTP_EOL;
  + ss << replaceIllegalCharsWithUnderbar(name) << printHierarchy() << c << PROM_EOL;
  }
  template <typename Vector>
  