IPv4-only mode saves 20KB+ of flash memory.
Add some backwards compatibility with the global Arduino Ethernet
class when running in IPv4 only mode.
Fixes#687
* Speed P.IO build by not cloning 2GB of sources
* Document P.IO new option
* Update board generation, use renamed function
* Update documentation with new platform integration state
* Remove accidentally pushed file
* Use correct update command
* Use correct highlighting
* Use correct language
* Add section on debugging
* Add docs on filesystem, minor corrections
* Use -iprefix in compilation, but still expose all include paths to IDE
* Add exception and RTTI support, document them
* Fix typo
* Add package.json
To make package easily integratable with PlatformIO
* Correct name back to original one
* Format package.json
* Add first shot at builder script
* Add USB stack flags, fix compile flags
* Formatting
* Add more link & USB flags
* Build Boot2 bootloader
* Formatting
* Generate linkerscript, linker fixes
* Fix linkflags, make firmware runnable
* Update USB flags and RAM size
* Correct USB flags, add dynamic sketch partitioning
* Restructure filesystem size and flash size logic into platform code
* Move C++ only flags to CXXFLAGS
* Add PlatformIO documentation
* Link to new platform.io document in the docs TOC
* Fix typos in platformio docs
* Fix one additional typo in platformio.rst
* Update docs
* Remove wrongly commited build folder
