All source files include general.h first and before anything else.
This inlcludes platform.h and platform_support.h
No header file needs to include to include any of these, but should include
any others needed for it's own declarations.
USB UART seems to work fine at 115.2Kbps or 230.4Kbps, but starts to drop characters
as the data rate goes higher. This commit changes the usbuart ISR to fill a software
FIFO, and adds a low priority timer interrupt to run deferred processing to drain a
FIFO and send USB CDCACM packets, rather than calling the usb send within the UART
ISR.
Tested on native platform, up to 1.5MBps.
