message: Replace old RFC1123 impl which cannot be built until GCC 5
diff: #include "common/common_headers_request_policy.hpp"
  #include <ctime>
  -#include <iomanip>
  -#include <sstream>
  namespace Azure { namespace Storage {
  @@ -29,10 +27,16 @@ namespace Azure { namespace Storage {
  #else
  gmtime_r(&t, &ct);
  #endif
  - std::stringstream dateString;
  - dateString.imbue(std::locale("C"));
  - dateString << std::put_time(&ct, "%a, %d %b %Y %H:%M:%S GMT");
  - request.AddHeader(c_HttpHeaderXMsDate, dateString.str());
  + static const char* weekdays[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
  + static const char* months[]
  + = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
  + std::string rfc1123Format = "%a, %d %b %Y %H:%M:%S GMT";
  + rfc1123Format.replace(rfc1123Format.find("%a"), 2, weekdays[ct.tm_wday]);
  + rfc1123Format.replace(rfc1123Format.find("%b"), 2, months[ct.tm_mon]);
  + char datetimeStr[32];
  + std::strftime(datetimeStr, sizeof(datetimeStr), rfc1123Format.data(), &ct);
  +
  + request.AddHeader(c_HttpHeaderXMsDate, datetimeStr);
  }
  return nextHttpPolicy.Send(ctx, request);
  