Ringbuffer

The new implementation use the mirroring method to distinguish full
buffer and the empty buffer. It also support buffers of arbitrary size.

usbdevice/core/core.c: fix garbage value bug

This could crash the program with -O1 and -O2 in MDK.

1.1.0 -> 1.2.0

1.1.0 -> 1.2.0

2006 - 2013 Copyright by rt-thread team

error: expected expression before 'void'
error: too many arguments to function

Use SRAM as EMAC transmit buffer, to avoid the underrun error, especiall...

Use SRAM as EMAC transmit buffer, to avoid the underrun error, especially in the large amount of data communication.

Dfs clean and optimized code

strip more characters in finsh token.

fix spelling error by ziyi897, this commit fixes #74.

Fixed At91sam9260 context switch issue, enable mmu, update SDIO and EMAC drivers

add avr32 bsp building to travis-ci