* Fix VM Address mask
Adjust VM Address mask to allow up to 8M Byte parts.
Allow for free heap size values over 64K
ESP.getHeapStats(, uint32_t,)
uint32_t getMaxFreeBlockSize();
* Fix example
* Update MockEsp.cpp for uint32_t on EspClass::getMaxFreeBlockSize()
* Added comment about heap size limitation and static_assert to verify.
Updated boards.txt to show correct External memory size and Heap size.