(bugfix service release)

IDE

• Fixed: IDE doesn't start if library_index.json is corruped.
• Fixed: IDE doesn't start if a library with invalid version is found.
• Fixed: Rare build errors in very complex sketches (like Marlin firmware).
• Fixed: Better dialog explaining that MacOSX 10.8 is now required. Thanks @PaulStoffregen
• Fixed: Slow "File" and "Tools" menus in MacOSX
• Fixed: Weird Board Manager behaviour if AVR core is downgraded to a version earlier than 1.6.22
• Improved first-use usability if the user don't select the serial port. Thanks @PaulStoffregen
• Custom "Tools" menu now keeps the order as defined in boards.txt.

Core

• AVR: Fixed EEPROM warnings. Thanks @bxparks
• AVR: Treat "narrowing conversion" as warning, not error. This will make some libraries
  to compile again. Thanks @PaulStoffregen