v1.4.5 - optimize decToHex() for specific platforms; add PrintStr::cstr() alternative for getCstr()

• 1.4.5 (2021-04-26)
  • Create more generic examples/AutoBenchmark program which replaces
    examples/Udiv1000.
  • Activate
    GitHub Discussions.
  • Add decToHexDivOnly() and decToHexDivMod() to AutoBenchmark, and
    update decToHex() to automatically select the faster one. On AVR,
    decToHexDivMod() seems to be 2 clock cycles (125 ns) faster. But on
    32-bit processors, decToHexDivOnly() is 2X faster on those without
    hardware divide (e.g. SAMD21, ESP8266), and 10-20% faster on processors
    with hardware divide (e.g. STM32, ESP32, Teensy 3.2).
  • Prevent overflow of uint16_t when calculating exponential decay average.
  • Add PrintStrBase::cstr() as a shorter, more convenient version of
    PrintStrBase::getCstr(). Retain getCstr() for backwards compatibility.
  • Upgrade to ESP32 Core v1.0.6 and regenerate MemoryBenchmark and
    AutoBenchmark.