Backported SPI Transcations from 1.5.x
Backported 'yield()' hook from 1.5.x
Backported Ethernet library from 1.5.x
Backported SD library from 1.5.x
Fix SPI transaction mismatch errors
Update revision log
Merge pull request #2365 from cmaglie/ide-1.0.x-spi-transaction

[IDE 1.0.x (backport from 1.5.x)] SPI Transactions