Merge from official Nuttx (http://git.code.sf.net/p/nuttx/git) "SHA-1: e8a979e5632ddb781c2da654c9f41990226ff83f (branch master) " 2013/8/21 08:06:04 AM

Signed-off-by: cctsao1008 <chiacheng.tsao@gmail.com>
Revert stm32_i2c.c to

Revision: a9fcb58d1adacffa644a61baafcdbe54e54389b9
Author: Lorenz Meier <lm@inf.ethz.ch>
Date: 2013/6/1 06:39:52 PM
Message:
Config improvements
----
Added: nuttx/arch/arm/src/armv7-m/up_stackcheck.c
Modified: nuttx/arch/arm/src/stm32/Make.defs
Modified: nuttx/arch/arm/src/stm32/stm32_i2c.c

Signed-off-by: cctsao1008 <chiacheng.tsao@gmail.com>