Merge pull request #469 from EmbeddedMan/master

A very minor re-ordering of USB interrupt initialization sequence to mak...
Merge pull request #470 from EmbeddedMan/master

Updated build.xml to use new (20140530) compilers. Also bumped build num...
Added volatile to some of the variable definitions in HardwareSerial_usb.c to prevent any possibility of the compiler re-ordering them and causing problems.